Category Archives: Reloading Corner

RELOADERS CORNER: Gas Port Pressure

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It’s not always possible to separate guns from loads, and there are some important things to know to get the most from your semi-auto. Here’s one! KEEP READING

casing in air

Glen Zediker

I have spent the last couple of segments taking a big step back recollecting my own (early) experiences and education as a handloader. Hope you’re happily indulging me, and hope even more that there’s been some good ideas that have come from it.

I started reloading as a matter of economy, and because I wanted to shoot more. Said then and said again now: if the impetus for reloading is saving money, you really don’t save money! You just get to shoot more for the same cost. Hope that makes sense, and likely you already understand that. Clearly, there are other reasons or focuses that attract folks to handloading, and personalizing ammo performance, improving accuracy, are leading reasons.

I’ve been at least a tad amount (to a lot) biased all along in my department topics toward loading for semi-automatic rifles. That’s been done for a few reasons, and the primary one is that, no question at all, there are specific and important details, a lot of dos and don’ts, in recycling ammo for a self-loader.

This is the reason I’ve been careful to specifically point out the “semi-auto” aspect of any tooling or preparation step. I’d like some feedback from you all with respect to your motivations and applications in handloading. Why do you do it?

Another reason is that, and I know this from much input, as happened with me 45 years ago, my interest in learning to reload came with ownership of a semi-auto that I absolutely loved to shoot! Here of late, my plumber, for a good instance, proudly announced to me outside the local hardware store that he had just purchased his first AR15 and showed me the paper bag full of .223 Rem. cartridges he had just purchased there. A scant few weeks later: “Could you help me get together some tools and show me how to reload?” I did.

Back to the focus, finally (I know) of this topic: what are those differences comparing semi-autos to anything else?

There are a few points, but one of the first, and one of the most important, is component selection. Case, primer, propellant. Propellant first.

AR15 gas port
As .224-caliber bullets get heavier, there’s a tendency toward many using slower-burning propellants. Often, the slower-burning fuels produce lower chamber pressures, which means more velocity potential (that’s true with just about any rifle cartridge). But! Gas port pressure will increase with slower and slower burning propellants. Can’t have it all, and make sure “function” is first on the list. That’s safe and sane function, by the way, not “over-function!”

I’ll assume, pretty safely, that the semi-auto we’re loading up for is an AR15, or some take on that platform. If so, it will have a “direct impingement” gas system. That’s a pretty simple arrangement whereby the gas pressure needed to operate the system, which cycles the action, is bled off from the barrel bore via a port. From there it goes through a manifold and then into a tube, and then back into the bolt carrier via the bolt carrier key. Gas piston operation is more complex, but what’s said here applies there also respecting propellant selection.

So, it’s kind of a wave. The idea is to get the wave to peak at a point where there’s not excessive gas entering the system, but there is sufficient gas entering the system. Mil-spec. 20-inch AR15 calls for 12,500 psi, for what that’s worth. And “piston” guns are nowhere near immune from concerns about port pressure.

The burning rate of the propellant influences the level of gas pressure at the gas port, and this, easy to understand, is referred to as “port pressure.” The original AR15 rifle gas system component specs (20-inch barrel, port located at 12 inches down the barrel) were created to function just fine and dandy with 12,000 PSI port pressure. Much less than that and there might not be enough soon enough to reliably cycle the works. Much more than that and the operating cycle is accelerated.

Port pressure and chamber pressure are totally separate concerns and only related indirectly.

Rule: slower-burning propellants produce more port pressure than faster-burning propellants. As always, “faster” and “slower” are relative rankings within a variety of suitable choices. The answer to why slower-burning propellants produce higher pressure at the gas port comes with understanding a “pressure-time curve.” A PT curve is a way to chart consumption of propellant, which is producing gas, along with the bullet’s progress down the bore. It’s what pressure, at which point. I think of it as a wave that’s building, cresting, and then dissipating. Slower propellants peak farther down the bore, nearer the gas port. Heavier bullets, regardless of propellant used, also produce higher port pressures because they’re moving slower, allowing for a greater build-up about the time the port is passed.

RE15
I put the (very safe) cut-off at H4895 burning rate. I’ll go as slow as RE15, and have with safe success, but its influential differences are noticeable. I can tell you that a 4895 is well within the optimum range to deliver intended port pressure (“a” 4895, mil-contract variety, was actually the early original 5.56 propellant).

To really get a handle on all this you have to picture what’s happening as a bullet goes through the barrel in a semi-auto, and keep (always) in mind just how quickly it’s all happening. Milliseconds, less than a few of them, define “too much” or “not enough.” As the bullet passes the gas port, there’s still pressure building behind it, and there’s more pressure building still with a slower propellant. After the bullet exits the muzzle, the pressure doesn’t just instantly go away. There’s pressure latent in the system (all contained in the gas tube and bolt carrier) that’s operating the action.

The symptoms of excessive port pressure come from the consequence of a harder hit delivered too soon, and what amounts to too much daggone gas getting into and through the “back,” the bolt carrier: the action starts to operate too quickly. The case is still a little bit expanded (under pressure) when the bolt starts to unlock and the extractor tugs on the case rim, plus, the increased rush of gas simply cycles the action too quickly. That creates extraction problems and essentially beats up cases. They’ll often show bent rims, excessively blown case shoulders, stretching, and so on.

Getting gas port pressure under control makes for improved function, better spent case condition, and less wear and stress on the gun hisseff.

There’s a huge amount more to talk about on this whole topic, and a good number of ways to get everything working as it should. But. For this, the most a handloader can do, and it’s honestly just about the most influential help, is to stay on the faster side of suitable propellants. Without any doubt at all, there will be rampant disagreement with my advice: no slower than Hodgdon 4895. Most all published data lists propellants from faster to slower, so find H4895 and don’t go below it. That’s conservative, and there are a lot of very high scores shot in NRA High Power Rifle with VARGET and RE-15, but those are edgy, in my experience, and define the very upper (slowness) limit.

m14 gas system
This doesn’t only apply to AR15s. The M1A is VERY sensitive to port pressure, which is also propellant burn rate. It’s a gas-piston gun. Same cut-off on burning rate is advised for these: H4895. I sho learned this the hard way by dang near wrecking my first M1A: bolt stuck back after firing a dose of H4350. That was before I met Sgt. Jim Norris and got the lecture I’me giving you. Thanks Sarge!

That alone doesn’t mean all AR15 architectures will be tamed (carbine-length systems are particularly over-zealous), but it does mean that port pressure will stay lower, an important step.

A caution always about factory ammo: some is loaded for use in bolt-actions (especially hunting ammo(, and might bea very bad choice for your .308 Win. semi-auto. AR15s are actually fairly more flexible in showing clear symptoms, some no doubt due to the buffered operating system and overall mild nature of the .223 Rem. cartridge.

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

 

RELOADERS CORNER: Blissful Moderation

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Glen Zediker recollects and reflects on the first advice he ever got on choosing a load: all things in moderation, pressure and velocity included! READ IT ALL

range load
When you just want to load up and go have a go at the range, there’s no need for speed. But! There is a need for enough pressure-power for reliable, clean function. I suggest trying something in the “medium” range for daily use. Your rifle, your barrel, your cases, and your senses will all thank you for reducing the shock by taking “two steps to the left” to find a load. Promise: you will not notice anything at all negative from any lack of “power.”

Glen Zediker

I spend a great amount of space in this department warning, and I hope educating, on the signs, signals, dangers of excessive cartridge pressure. That’s all been and being done because, for the majority, maximizing velocity is an ammo-goal. Hunters, varmint and game, competitive longer-range shooters, usually want the most they can get from bullet flight performance, and also impact strength.

For me, there’s zero doubt that more speed is a better score on a full-length NRA High Power Rifle course. (Side note: it is a fallacy that lighter loads are more accurate. They’re not, or not because they’re lighter. Some of the best perforations I’ve seen are with maxed loads.)

But! I shoot a toned-down load for reduced-distance courses (as well as for the 200-yard events on full-length), and my general-purpose clods-and-cans load is a lower-stress recipe.

I mentioned last time that I had recently fired a good deal of current NATO-spec ammo and was, I guess “impressed” is the right word, with its power level. The stuff I make up for afternoon fun-runs is a good deal less stressed.

I’m not at all recommending a “light” load. Just let’s call it a solid “medium.” Looking over my notes for the past umpteen years, going through my last most current load-data notebook, I saw what was to me an interesting happenstance. I tended to be pretty much right at one-and-one-half grain less than maximum (and about two grains with .308-class rounds).

dirty case
Signs of a load that’s too “light” include, clearly, one that won’t cycle the action reliably on a semi-auto. Another couple, for any action type, include an unusually dirty chamber and sooted-up cartridge case necks and shoulders. A little lighter still and you might see a primer that’s backed out a tad. Those all result from the case not expanding fully to seal the chamber forward and stretch to comply closer to chamber dimensions end to end. A little reduction won’t normally show any of this, and, tip: go a tad toward the faster end of suitable burning rate for general use.

Thats not a light load! It’s “three halves,” three one-half grain drops. That half-grain, and some might recollect my mentioning this a few times in the past, is my always-recommended “come-off” step for any pressure sign (not a tenth or two, but a “full” half grain). Any other over-pressure indicator from that point then signals need to come off another “full” half-grain. So I pretty much come off those two halves from the get go, add another, and, guess what? Never nary a pressure concern.

Slightly faster-burning propellants, in my experience, lend themselves better to the “medium” power level reduction in terms of maintaining accuracy. As always, “faster” and “slower” are values within a small range of propellant rates suitable for a particular cartridge and bullet. And, in following this plan, when needed bump it up to full speed with predicatable results.

For .223 Rem.-class cartridges, a half-grain is worth ballpark 40-50 feet per second, again depending on propellant.

The advantages of a “medium” load are predictable, but here’s my list: plain old easier on the gun, and on the barrel, and on the self. Again (and again) I’m not talking abut a “light” load, just one that’s maybe 95-percent, a solid 150-200 feet per second less than published maximum. Case stress will be reduced, and that’s associated with length trimming frequency and overall “life” before primer pocket enlargement and general stretch-thinning, cracking symptoms retire the brass.

Back to my “story,” which was the interesting happenstance (all this was all brought back to me by the initial outing with my new old AR15 I talked about last edition, and my 16-year-old son asking me if I could teach him how to reload because we ran out of ammo so quickly…): So. When I first learned to reload I was 15. This event coincided with my first AR15 rifle, which was purchased new at a Skaggs drugstore. Right. My mother did not eagerly agree to sponsor a reloading setup, but, being a wise-enough woman, did interpret the math the same way I did: I could shoot a lot more for a lot less if I was doing my own. So, I had a friend, Gary. Most fortunate man to know. Gary, and I see this more clearly each year that passes, knew more about guns and shooting than any 10 people I have since encountered.

We went to Bald Bob’s Sporting Goods in Rifle, Colorado. He chose an RCBS kit for me, a piece at a time. Bob sold RCBS only. Press, dies, scale, meter, case lube, doo-dads, and, of course some propellant and brass and bullets and primers. And a Sierra Bullets loading book. So, back home, and a short time later, there I sat before my new array of green pride-and-joys. After stern lectures about things I was never supposed to do, and at least an equal number of things I was always supposed to do, we got this show flowing downriver.

Gary had chosen IMR 4198 for me for a propellant. He said it was clean-burning and economical. Didn’t take much of it. I had some Speer 55-grain full-metal-jacket bullets, some Remington cases to go along with the empties I had saved in a paper bag, and some CCI primers. Now. We looked at the loading tables in the Sierra Manual, and he had me find my cartridge and bullet. (He already knew exactly where we were going, so this was for my benefit.) He pointed out the “maximum” load and the “starting” load, one on the far right and the other on the origin point of the table on the left. He then counted back two places from the far right: 20.5gr. He said, “There. That’s the one. It’s not going to give you any troubles, and it’s adequate for function.”

“That was easy,” I thought.

I have since learned that advice was too good not to share.

If you’re looking for a good load, and you know the propellant is wisely-chosen, going two steps down from the manual-listed maximum should, indeed, be a great place to start, or to stay if you are sans chronograph. Time after time, I have noticed over the many, many years I have now been doing all this, that the “two steps back from max” procedure is safe, sane, and satisfying.

reduced load list
Here’s a page (“the page”) from my now-ancient Sierra manual. Not all manuals agree (not nearly) on max loads, and not all are done in multiple increments, but the essential advice is reducing the max load by two steps, or about one-and-one-half grains of propellant in this case (reduction amounts vary, certainly, based on the cartridge). It’s wise advice from a wise man, and I’m talking about Buddy Gary. I just pass it along because it sho works for me!

I shot about a gozillion rounds of 20.5 grains of 4198 through that SP1. Since it was not a max load, I could also change the bullets without worry, going from one brand to the next at the same weight, of course. I could change cases and even primers. It was a tenth shy of one-and-one-half grains under maximum. I don’t recollect ever grouping that rifle on a paper target. I zeroed it based on preference and I also don’t recollect ever missing anything I aimed at by more than a little bit, and never twice.

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: 5.56 NATO: “GO,” “NO-GO”

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This “warning” has been around, and around, for years, but it’s still not always heeded, or understood. Read why and how it matters HERE.

nato stamp
The circle-cross stamp is a NATO-spec cartridge. Your barrel might be marked “5.56” or a more lengthy disclosure referencing its specs. If it’s “.223 Rem.” do not fire a NATO round through it! Your barrel might also not be marked at all. I’ve increasingly seen that. Get it checked. A NATO round will chamber perfectly in a .223 Rem. All exterior dimensions are patently the same, again, it’s the pressure level.

Glen Zediker

I know this is “Reloaders Corner,” but, every now and again at least, I rip open the end of a cardboard factory cartridge box, or five.

I just got finished building up a “retro” AR15 for a new book. Reasons for that are a few, but probably the main one was that I wanted to recollect the one that “got away,” well, the one that I let go. Errant short-sighted judgment, as is common in youthful people. So I built a replica M16A1, circa mid-60s, well, of course, with only two selector stops. At the heart of that rifle is an original-spec barrel, chrome-lined, NATO chamber.

5.56 stamp
This is a NATO chamber stamp. If it’s “.223 Rem.” that’s NOT the same!

That’s leading to this: I opened up a few boxes of “genuine” NATO 5.56 to check it out with, something I honestly haven’t fired for years and years. Dang. That stuff is potent. Over the past several years, the pressure level has increased. Current standard is a little over 62,000 PSI. (NATO is technically measured differently than commercial, but the figures I give here are accurate for comparison.) Compared to SAAMI specs for .223 Remington (commercial) that’s a solid 7,000 difference. (That SAAMI-spec figure has likewise increased over the years, judging from recent test figures I’ve seen respecting commercial .223 Rem.; most references heretofore were max at 52,000 PSI.)

The main impetus for this article, though, came from a recent experience at a local gun shop. I went in search of a sub-sonic .300 Blackout load, and they had one in .300 Whisper. The counter person told me that it was “exactly the same as .300 Blackout, just like .223 is the same as 5.56…” Whoa. Neither statement is true, although Whisper specs are plenty close enough to Blackout that no differences factor in safety or function. However! I didn’t take the time to lecture, but, dang, .223 Rem. and 5.56 NATO are not nearly the same.

First point: do not fire NATO-spec ammo in a rifle with a chamber marked “.223 Remington.” It will, not may, be over-pressure. Reasons have to do with chamber specifications for 5.56x45mm NATO and those for SAAMI-spec .223 Remington. There is a significant difference in the leade or “freebore” cut comparing SAAMI to NATO. That’s the space in a chamber ahead of the cartridge case neck area that leads into the rifling. NATO is radically more generous, meaning “bigger”: longer, more volume. (About 0.150 inches, based on my measurements of bullet seating depths that touch the lands.) There is relatively much more room for expanding gases to occupy in a NATO chamber. In a SAAMI chamber there’s much less room for expanding gases to occupy. The additional pressure is about the equivalent of another full grain (or more) of propellant in the case. Yikes.

high pressure nato
Here’s what happens putting a factory-fresh NATO round through a .223 Rem. chamber. This case is clearly beat. Sure, it might, should, hold up for that firing, but the case is done and the gun took a needless hammering.

nato beat case

There are other little nit differences to pick between the SAAMI and NATO cartridge, and, therefore, chambering specs, but they don’t really factor in a material sense. There’s bound also to be just as many small differences in cartridge dimensions from one maker to the next. I’ve measured enough to tell you that’s true.

Now. What this has to do with reloading (finally, I know) is based on a question I’ve gotten over the years, a concern to some, or at least, as said, a question. And the answer is that you’re better off going with .223 Remington loading data for any ammo intended for “general” range use. That means blasting away on an afternoon. Just because it’s a NATO chamber does in no way mean you’re supposed to run NATO-spec ammo through it! Back it off and enjoy it more.

If you’re relying on a factory-published data manual to give a place to start, or stop (something from Sierra, Hornady, Lyman, or so on) pay very close attention to the test barrel specifications. Clearly, barrel length has a big influence on attaining the published velocities, and some load combinations are going to be worked up using considerably longer barrels than what the most of us have on our AR15s. But the biggest factor is the chamber used in the test barrel. If it’s a SAAMI-spec (sometimes called a “SAAMI-minimum”) chamber then the data should be on the conservative side. Should be. Do not, however, bank on any idea that you should jump straight to the maximum load listed if you’re loading for use in a NATO. There are, always, too many factors that otherwise create more or less pressure (primers, cases, propellant lot, and more).

As time goes by it probably is less likely to encounter a semi-automatic “.223” that’s not a NATO, but it will be marked as such! Clearly, most ammo is used in the most popular guns. That’s not going to be a bolt-action anymore. Make no mistake, though, AR15s exist plentifully that have SAAMI chambers, and I see a lot of aftermarket barrels that are cut with that minimum-dimension reamer.

ANOTHER OPTION
So what’s a “Wylde” chamber? This is a chambering spec developed by Bill Wylde, one of the early and leading pioneers in the quest for improved AR15 accuracy. It is popular and available, especially in aftermarket barrels. What it is, is a chamber that’s in-between SAAMI-minimum and NATO, leaning closer to NATO. Rumors are true: it’s safe to fire NATO-spec factory loads through a Wylde. The Wylde was designed upon the introduction of the heavier competition bullets with the idea of providing more freebore to accommodate the necessarily longer cartridge overall lengths necessary with something like an 80gr. Sierra, but keep the amount of jump to a minimum with shorter bullets fed from the magazine.

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: Why Not Flat-Base?

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A better question, given that the vast majority of popular rifle bullets are boat-tail, is why flat-base? KEEP READING

flat base bullet

Glen Zediker

Good question! I have something that at least has elements of an answer.

A boat-tail bullet is the standard for the majority of rifle bullets, and the domineering choice of long-range shooters. Competitive Benchrest shooters favor flat-base bullets. Flat-base is also popular with varmint-hunters: the stellar Hornady V-Max line for good instance.

Hmm.

We all want best accuracy, so why the difference? Consider the overriding characteristic of a flat-base bullet: it’s shorter. Now, since not all flat-base bullets are shorter overall than a same-weight boat-tail (they’re usually not), I seriously need to clarify that!

Clarification: a flat-base can be shorter, and lighter, than it would be if the same ogive or nosecone profile used then added a boat-tail. More: if they’re both the same weight and at least similar in profiles, a flat-base often has a longer bearing area than a boat-tail bullet, again because the boat-tail is sticking down there, or not. These are both a bonus to Benchrest or any other shorter-distance circumstance where utmost precision is the goal. (When I refer to capital-b “Benchrest,” I’m not talking about a shooting rest, but a competitive sport.) Shorter bullets allow slower barrel twists (bullet length, not weight, chiefly governs needed twist). Slower twists offer a miniscule improvement in damping a bullet’s orbital pattern in flight, and considering the likewise near-caliber-size 5-shot groups these folks are after, that matters. Bullets fly in a spiral, like a well-thrown football. Again comparing those with similar profiles, flat-base bullets stabilize faster and sooner than boat-tails, it’s a smaller spiral. Bullets with longer bearing areas tend to shoot better “easier,” less finicky. And, flat-base bullets can provide more cartridge case capacity.

vld and ld compare
Here’s unique. Jimmy Knox of the original JLK Bullets once made flat-base versions of his Davis-designed VLD (very low drag) boat-tails. So this is a .224-caliber flat-base 65gr LD (low drag), which is the same as his 80gr VLD shown with it, just no boat-tail. Why? It was more of a “Why not?” Idea was to provide better downrange performance for those with slower-twist-rate barrels, and to retain the flight pattern and in-barrel characteristics he liked about flat-base (and way on more speed). This idea was popular among some better High Power shooters about 15 years ago.

All those good points make it sound like flat-base provide superior accuracy. They might. By my experience, they do, but! Distance defines the limit of that truth.

The boat-tail provides an aerodynamic advantage, and the farther it flies, the greater this advantage. There are well-founded beliefs that boat-tails are less influenced by gas pressure thrusting against the bullet base. A good and most knowledgeable friend at Sierra told me that a boat-tail has an effectively more concentric radius at the base due to the junction point created by the angle on the tail and the bearing surface. Further, a flat-base, is, in effect, harder to make so that the base will have a radius that’s as concentric with the bullet bearing surface. Manufacture care and quality (related), of course, makes that more or less true or false. If the idea is that a good boat-tail is “easier” to make, that this shape makes the end product more forgiving of manufacturing errors, then I’ll accept that since it’s pretty hard to argue against, but, again, I really don’t think that boat-tail designs simply take up slack in quality tolerances. I’m sho no rocket-surgeon but I know that the tail slips the air better.

LD_ and Hornady 68
Same LD bullet compared to a Hornady 68gr HPBT. The 65 is a tic shorter overall but, because it’s a 15-caliber (!) ogive, way less bearing area (exception to the “rule” big-time) than the boat-tail next to it. The 65 had a higher BC but was über-tricky to get to shoot well. I could get these to just over 3000 fps in a 20-inch .223 Rem. Mostly because of the tiny bearing area.

This can get pounded completely into the ground because adding a boat-tail (and I’ll show a great example of just that) to a similar nosecone also adds weight to the bullet, and that increases BC. It’s not exactly a chicken-egg question, though, because the tail helps otherwise.

barts bullet
Here’s a 52gr boat-tail from Hornady (right) next to a 52gr custom Benchrest bullet. I said the overriding difference is that a flat-base bullet is shorter, but that’s not referring to overall length. A flat-base is shorter than it would be as a boat-tail, if the other dimensions were the same, and usually has a longer bearing area.

You might have also heard said that boat-tails shorten barrel life because the angled base directs burning propellant gases more strongly at the barrel surface. They do, and many steadfastly uphold that as a reason against them. More in a bit. However! Beyond 300 yards, at the nearest, there are no disadvantages in using boat-tail bullets that come close to surpassing their advantages.

There’s another debated advantage of a flat-base and that is they tend to shoot a little better in a barrel that’s about to go “out.” I’m talking about a good barrel that’s pushed the limit of its throat. That one is true too!

And speaking of barrel life, another is that flat-base bullets produce less flame-cutting effect than boat-tails. A barrel lasts longer if fed flat-base. True! Flat-base bullets “obturate” more quickly. Obturate means to “block,” but here it means to close a hole, which is a barrel bore, which means to seal it. The angled boat-tail creates a sort of “nozzle” effect. Can’t much be done about that, though, because when we need boat-tails we need them. That is, however, a big score of help for the varmint hunter.

There is a relatively obscure “combo” out there called a “rebated” boat-tail. This has a 90-degree step in from the bullet shank (body) to the tail. It steps in before the boat-tail taper is formed (they look like a flat-base with a boat-tail from a bullet a couple of calibers smaller stuck on there). It’s common for competitive .308 NRA High Power Rifle shooters, for instance, to switch from the popular Sierra 190gr MatchKing to a Lapua 185 rebated boat-tail when accuracy starts to fall off due to throat wear. Sure enough, the Lapua brings it back for a couple hundred more rounds.

rebated boat tail
Here’s a rebated boat-tail. 115 grain 6mm from David Tubb.

If anybody with heavy equipment making bullets for sale out there is listening: I’d like to see some more rebated boat-tail designs! It is, though, a challenge to make precisely.

So. What? So what? Well, if you are big into small groups, I very encourage some experimentation with flat-base bullets. Again, distance is the only limit to their potential goodness. 100 yards, yes. 200 yards, yes. 300 yards, no!

vld chamfer
One thing is for certain: Flat-base bullets are not nearly as easily seated! Some have an edge-radius, some don’t, but, they are very easy get started crooked, or difficult to get started straight, same effect. I strongly recommend taking steps to square case mouths and use a generous chamfer.

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: What I do…

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There are a lot of ideas and options when it comes to loading the “most important” ammo. Here’s the 5-step process I ended up with… READ MORE

dial indicator

Glen Zediker

I spend a lot of time telling everyone else what they should do, and probably more time telling them what not to do, or what they could do… I thought it might be best to tell you all exactly what it is that I do to prepare a batch of ammo for a tournament.

That’s a quick way to show you what, clearly and obviously, matters to me. I admit: I don’t always do all the things that I talk about. A big part of my role here is to pass along information, answer questions before they’re asked, in a way of looking at it. There’s information, and then there’s action, and that’s not a contradiction, to me. For instance, I can tell you all about case neck turning, and metplat uniforming, and many other preparation steps. I have done them all, sometimes do them, but dang sho not always.

Believe me: I have tried everything and much, much more than I’ve ever talked about in these paragraphs.

Following is what I have found works to my satisfaction. Since I’m dealing with a fair amount of cartridges at any one time, there is, no doubt, a time and effort element that’s important to me. In other words, what’s coming next are the things I really think I must do to give my score the best boost I can reasonably give it.

Step One: Get my cases together and size them. I load in 100-round batches, so I start with five boxes, or whatever corresponds to 100 rounds. Without so much as a second glance, I run them all through my full-length sizing die: lube each and cycle it through. If nothing else, most new cases are not nearly ready to load. The case necks are usually banged up, not round, so at the least I’d need to size the inside and outside of the case neck, and I’ve found that, while other appliances will suffice for that, it’s just easiest to use my sizing die.

Step Two: I trim them all. This isn’t done as any matter of safety, just consistency. I set my trimmer to at the least touch each case mouth. This is very important! The next prep steps rely on having cases that are all the same length.

case trimming

Step Three: After chamfering inside and outside (I use a 17-degree on the inside and a standard tool for the outside) I run a flash hole uniformer through each. This is why it’s important to have them all the same height. That way the uniforming tool cuts to a consistent depth.

inside uniformer
After full-length sizing all my new cases (to mostly get the necks shaped up), I trim all the cases to ensure length consistency to start, because the next procedure, inside flash hole deburring, demands it. Shown is from Hornady. CHECK IT OUT HERE

Step Four: Primer pocket uniforming. I run each through this process. Now, I have had some lots of brass that make this normally simple process a chore, and that’s because the reamer is too snug a fit to the pocket. We all know that primer pockets are at their smallest on new cases. That is, by the way, one reason I’ve mentioned that the primer pocket “feel” is a leading indicator after the first firing as to the pressure level of the load. In keeping, there are times when I wait until recycling the first-fired cases before running the uniformer. It depends on how readily the cases will accept the reamer.

primer pocket reamer
Primer pocket uniforming is an important step in my own process, but sometimes I wait until the first-firing. Depending on the tool used, and how much power can be applied to assist, this job can be a chore on a tight pocket. Shown is a Lyman tool. CHECK OUT TOOLS HERE

Note: I consider my “best” ammunition to be that which I load on my once-fired cases. At the same time, I won’t hesitate to use new cases for a tournament (but not for a Regional or bigger event). Over a whopping lot of time keeping notes, my “second-firing” rounds tend to shoot a tad better, but it’s a miniscule amount. That’s why I don’t really sweat over the primer pockets on the first go-around.

Step Five: Roll them all! I run all the cases through a concentricity fixture, aka: spinner, to check runout. I segregate on the following criteria: “flatliners” no visible runout, less than 0.001, 0.001, up to 0.0015, more than that… Five piles. One reason I do 100-round batches is because I need, technically, 88 rounds for a tournament. Since I am using “name-brand” brass, I easily find my 44 prone-event cases that are going to be no more than 0.001 out of round. The remainder are proportioned better to worse for the 200 yard events. It’s not that I don’t think each round matters, because it does, and, honestly, the 200-yard Standing event is what wins a tournament, but that’s way on more on me than the ammo. A case with 0.015 runout is not going to cause a “9.” That case will produce groups way inside the X-ring.

Co-Ax Case and Cartridge Inspector
I segregate using a runout indicator, a tool shown before in these pages. Some argue, logically, that the best way to find cases with the most consistent wall thicknesses is to measure wall thickness, but, my experience has shown that, ultimately, concentricity is the result of wall thickness consistency. Sho is faster. Shown is a Forster Co-Ax Case & Cartridge Inspector

Now. I fully realize that segregating by runout, concentricity (“centeredness”), is not the same as actually measuring case neck wall thicknesses. However! “Flat-liners” are what ultimately result from consistent case neck walls. Since I have also sized the inside of the case neck, not just the outside, the spinner does give an accurate indication of case neck wall consistency.

case segregation
After sorting by runout, here’s what I get, or what I got once… These were graded (left to right) 0.0000 (no perceptible runout), up to 0.0010, 0.0010, 0.0015, and more than that. So, here, there were 37 cases that were at or near the level of neck-turned cases, and another 37 showing only 0.001, but way on easier.

Since it’s often the night before that I’m doing this, spinning is way on faster than measuring…

Then I prime, fill, seat. Get some sleep.

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: Meter Use Tips

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How well you set up and operate a powder meter has a lot to do with ammo consistency. Here are a few tips on getting the most from this tool. READ MORE

Glen Zediker

Going back to our last conversation, the topic was dispensing propellant charges, and whether to weigh each charge or dispense each charge using a powder meter. Generally, most seem to agree that weighing each is the sure way to better consistency. I don’t always agree with that, and I say that mostly because my chronograph and group size numbers don’t support superiority of either approach. However! I sure do know that metering charges is way on faster and easier than weighing them all out!

Once again: the only answer that works is to experiment for yourself and settle the question based on empirical evidence. Right: shoot it and see!

This next offers a few tips I’ve had good success with over the years. I can tell you that, without any doubt, learning how to set up and operate a meter has a decided influence on those chronograph and group size measurements.

scale weight
I am adamant about following this process to set a meter: Don’t throw and weigh single charges to adjust the meter. Throw and weigh 10-charge portions, with the scale set, of course, to 10-times the desired single-charge weight. I do not recollect one time when my meter adjustment did not change following this process from what I first arrived at weighing single throws. Here’s how I set it to adjust for a 24.0 grain throw.

First: I very strongly recommend setting the meter throw based not on one single charge, but on multiple charges. Here’s my method: After running a few single throws to get it close, I set my scale to 10 times the desired single-throw propellant charge weight, then throw 10 charges into the scale pan. I have done this (so) many times over (so) many years that I can tell you that I have no memory or record of this tactic not influencing the final setting I have dialed in. Do this 3-4 times and see what you see. There’s a huge likelihood there will be an adjustment needed. And for some reason, supported by my notes at least, the final setting is usually a tick lower than I gauge for one-throw-at-a-time weight checks.

Now, I know that if the meter is accurate then each single charge will weigh what it should, but maybe the difference that makes this method work best is that scales aren’t perfectly accurate. Maybe it’s the damping system, or continual issues with calibrations, but a 10-throw lot ultimately results in a more precise setting. I’ve proven that too many times to myself to qualify it with a “may.” No, it does.

As mentioned in a past article, the smaller the propellant granules the more precise each fill can be. Longer-grained kernels provide more air space and “stack” more than smaller-grained kernels. It’s also clear that the higher degree of precision on the meter internal sliding surfaces, the more “clean” the strike-off will be.

And, meter operation has a whopping lot to do with the consistency of filling the meter drum. Just like tapping a case bottom settles the propellant to a lower fill volume, same thing happens filling the drum in a meter.

powde meter operation
Not too heavy, not too light. Work the handle the same each time, and have it come to a positive stop. “Thunk. Thunk.” Focus on a consistent speed. This has a huge effect on how consistent the throws will be.

The trick to good throws is working the meter handle consistently, and also settling on a contact force when the meter handle comes to a stop in the “fill” direction: It should bump but not bang… I wish I could be more clear on that, but it’s a feel. Don’t go too slowly, gingerly taking the handle to its stop, and don’t slam it there either. You want a positive, audible “thunk” when the handle stops. If it’s the same each time, fill consistency will, not can, improve. Focusing on operating the handle at a constant rate of speed teaches this in short order. It’s a positive movement that, for me, takes about one second to lift the handle.

harrells meter
I recommend longer drop tubes (meter or funnel). The longer tube has the same effect as tapping the case to settle the propellant. This helps in loading stick propellant into small-capacity cases. Rubber-band a dryer sheet around the propellant container to static influence, which can be an influence, especially in the Western regions.

There’s a few more tips in the photo captions, and here’s another: Do not leave propellant in a meter! Return it to a sealed container when you’re done for the day.

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

 

RELOADERS CORNER: SD Pt. 2

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Here’s how Standard Deviation calculations can figure in ammo decisions (or not…) READ MORE…

Glen Zediker

Seems like the last couple of articles on load testing and velocity data got some pretty good responses and attention, and so that means there’s more! Of course there is…

As said, Standard Deviation (SD) plotted out forms a bell curve. A bell curve indicates the “probability density” of the normal distribution, or range, for something like velocity consistencies. For our purposes that’s the likely speed of the next shot.

Chances are outstanding that running all the numbers gotten from a chronograph session will plot into what’s called a “normal curve.” Like any normal bell curve, it gets divided into three segments and values, and these divisions are the “standard deviations.” And remember it is “a” standard deviation.

(I’ve said many a time that I’m sho no mathematician, and I am aware that there’s more and different ways to apply and model a curve, and to manipulate standard deviation results for different applications, but I’m trying to keep it more simple and use this “normal curve” for examples, it’s also called “population standard deviation.”)

We’ve been working with the right-respectable SD example of 12.

standard deviation curve
Here’s the same old curve I’ve been using, but at least in a different color!

Assuming that normal curve, the distribution of “some number” of shots is forecasted like so: some 68 percent will lie within 1 standard deviation of the mean, about 95 percent lie within 2, and over 99 percent lie within 3 standard deviations. Again, since our SD is 12, then about 68 percent (approx. 2 out of 3) of all “next shots” will be +/- 12 feet per second. Since, though, the curve is in threes, that means that a scant number of the shots pose a chance for +/- 24 and some much (much) smaller chance remains for some shots to go to +/- 36. SD estimates how likely it is for those “head-scratchers” to show up, and also what might be the most realistic extreme any shot can deviate.

Data is a record of numbers and I do know that there’s 100-percent chance that the highest and lowest velocities collected for an SD calculation did, in fact, happen. To me, that’s what matters. No matter what the collected shot results calculated into for an SD, those were the two that represent the highest and lowest prints on the target.

It’s mathematically not possible for an SD to be higher than the greatest single measured deviant, and an SD can sho be lower than any single “bad” shot. Given how it’s calculated, along with how many samples contributed to the calculation, it’s plain that the nearer the majority are to themselves the less impact a bad one or more has. The more input the better.

ppc
Cartridge choice has a whopping lot to do with it! Some cartridges are seemingly destined (designed really) to produce better velocity consistency. Many magnums, for instance, are notoriously sporadic, while others, like the 6XC or one of the PPC cartridges (shown), seem to deliver constant velocities without a lot of special effort. It all has to do with internal ballistics and “efficiency,” and architectural analysis I don’t claim to understand, but I do know that’s one of the reasons 6XC holds the NRA High Power Rifle Long Range record, at the hands of David Tubb.

Many of us have heard or read the frequently-sung “…seen good accuracy with high SDs…” And we’ve probably also all decided that can’t be taken at literal value. Well, it can’t. Three things: what is “good accuracy” to this fellow, at which distance were the groups printed, and what’s he say is “high,” because without knowing these things there’s no accounting for the accuracy, believability, or interpretative definitiveness of what’s being said. So I say it’s 12. A 12 should not be responsible for a points loss, also considering the edge limits of usual group size. Getting into more and more numbers derived from more and more “what if’s” plotting out bullet trajectories and wind drift amounts, and, always assuming a consistent bullet ballistic coefficient demonstration (also not likely) running “12” through all these mathematical-hypothetical scenarios will show that 12 doesn’t lose many, if any, points.

One last that isn’t really a strong point, but is a point… If we’re shooting something like a .223 Rem. then a half-grain is about 40 feet per second. If that 12 SD shows its worst and pops one out +36 feet per second, to me that represents something akin to a pressure spike (logic dictates that more velocity had something to do with more pressure). I know my loads are running a tad amount edgy, and seeing a small velocity variation is likewise a tad amount more reassuring that a primer won’t go over the edge.

tubb 1000 yard clean
Here’s the ultimate result of low velocity deviations. It’s up to the shooter to apply the left and right, but it’s up to the ammo to keep vertical stringing to a minimum. David Tubb does a stellar job on both. 1000 yards, fired prone with a scope. 6XC.

TESTING TIP
If you’re testing much beyond 200 yards, and especially beyond 300, pay no mind to the left and right, but keep a close watch on the up and down. In ideal conditions, groups are supposed to be round (I’m convinced they’re actually square, but there’s no need to go into that). If there’s any wind, don’t even try to correct for it (as long as impacts are on the target). I honestly don’t need a chronograph to confirm load consistency if I’m seeing small vertical dispersions. I’ll already have speed-checked the load I’m down on the mat with, and, again, I’m just wanting to see how level I get my perforations. If I come out with a 600-yard group that’s a foot wide but only three inches tall, I’m happy.

6 TIPS FOR LOWER SDs
Aside from finding the perfect and magical load combination, ha, there are a few things that do seem to help tighten shot-to-shot velocity deviations. They’ve all be talked all the way through and back again in this space in other articles, but, considered ultimately that this is the overall effect they have, here they are again:

One. Primer seating: fully seated onto a flat pocket bottom.

Two. Consistent propellant charge: weigh the charges if metering isn’t dead-on.

Three. Ignition efficiency: consider trying that inside flash hole deburring routine…

Four. Consistent case neck sizing, and, believe it or not, about 0.003 worth of “tension.” Don’t go too light…

Five. Temperature insensitivity: choose propellants that exhibit stability under extremes.

Six. Balance: strive to find a propellant that fills the case, but “loosely” (no compressed charges); even more, avoid an overage of air space. These both allow too much variance in ignition pattern.

inside deburring tool

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: Standard Deviation

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Improving longer-range accuracy has a lot to with consistent bullet velocities. First comes understanding it! Here’s a start on it… KEEP READING

chronograph

Glen Zediker

It’s springtime (finally) and one of the things on your list might be working up a load for a new rifle, or new bullet. I’ve talked about testing processes and procedures, and also some about those bullets, and especially those with higher ballistic coefficients. The more aerodynamic bullet, by itself, is no guarantee of a smaller group (and whether you’re shooting one shot or 20 shots, you’re always shooting a group…).

To make the “magic” of a high-BC bullet come to life, they all need to be arriving at the destination at really close to the same speed. On target, that’s all about elevation consistency. It’s pretty commonly accepted among long-range competitive shooters that points losses come more from errant high and low impacts than from missed wind calls. High-BC bullets traveling at more consistent speeds reduces dispersions in all directions. But only if they’re traveling at consistent velocities!

The first step to improving velocity consistency is getting a good way to measure it. That there would be a chronograph. Nowadays especially, there are a number of simple-to-use and inexpensive chronographs available, that are accurate. Some have more features, which mostly revolve around providing printouts, digital records, and calculations, but what matters most (to me at least) is one that lets me easily read the velocity of each shot.

Check Misdouth offerings HERE

MagnetoSpeed
The newer barrel-mounted electro-magnetic chronographs make it really easy. I like the idea of being able to chronograph from shooting position, not just from a benchrest. This is a MagnetoSpeed.

So. What’s next is understanding the terms associated with this area of data-gathering.

“Standard deviation” (SD) is the most common measure of shot-to-shot consistency. It reflects on the SD reflects on the anticipated consistency of bullet velocities (some number of recorded velocities). The “standard” part reflects on a sort of an average of the rounds tested.

[Phrases like “sort of” upset mathematically-oriented folks, so here’s the actual definition: SD is the square root of the mean of the squares of the deviations. More in a bit.]

I pay less attention than many to standard deviation because: I don’t think standard deviation is near as important as is the “range,” which is the lowest and highest speeds recorded. Another that matters is “extreme spread,” which, by definition, is the difference between this shot and the next shot. I watch the speed on each shot. I compare this one to the next one and to the last one, and, as said, find the highest and the lowest.

Why? Well because that’s how I shoot tournament rounds. This one, then another, and another. A low velocity difference means that the accuracy of my judgment of my own wind call has some support.

standard deviation
Standard deviation calculation forms a bell curve. The steeper and narrower the apex of the bell, the narrower the fluctuations were. But there’s always a bell to a bell curve and the greatest deviations from desired standard are reflected in this portion of the plot. Depending on the number of shots that went into the SD calculation, these deviations may be more or less notable than the SD figure suggests. So? Watch each shot. That’s the way to know how a load performs with respect to velocity consistency. SD allows you to estimate how likely it is for “outliers” to show up.

A load that exhibits a low SD is not automatically going to group small, just because a low SD. I’ve had Benchrest competitors tell me that sometimes their best groups don’t come with a low-SD load, but do not apply that to greater distance! At 100 yards a bullet’s time of flight and speed loss are both so relatively small that even what some might call a big variation in bullet velocities (+/-25 fps or so) isn’t going to harm a group, not even the tiny groups it takes to be competitive in that sport. On downrange, though, it really starts to matter. (And keep in mind that “it” is a reference to velocity consistency, whether denoted by SD or otherwise.)

For an example from my notes: Sierra 190gr .308 MatchKing. Its 2600 fps muzzle velocity becomes 2450 at 100 yards and 1750 at 600 yards. (These numbers are rounded but serve for a example.)

If we’re working with a just awful 100 fps muzzle velocity change, that means one bullet goes out at 2550 and the next leaves at 2650, in the worst-case. The first drifts about 28 inches (let’s make it a constant full-value 10-mph wind to keep it simple) and the next slides 26 inches. But! Drop… That is THE factor, and here’s where inconsistent velocities really hurt. With this 190, drop amounts over a 100 fps range are about three times as great as drift amounts. This bullet at 2600 muzzle velocity hits 5-6 inches higher or lower for each 50 fps muzzle velocity difference. That’s going to cost on target, big time. And it gets way, way (way) worse at 1000 yards. Velocity-caused errors compound on top of “normal” group dispersion (which would be group size given perfect velocity consistency). Now, it’s unusual for a wind to be full-value and dead constant, so on-target left and right displacement is even relatively less — but elevation displacement is consistent regardless.

So, my 100 fps example is extreme, but half of that, or a quarter of that, still blows up a score, or an important hit on a target.

propellant charge consistency
This is probably the most influential factor in improving SD: consistent propellant charge. It’s not only that each case has an identical powder load, though, because primer factors, and finding the right combination ultimately is why we do all the testing…

So what’s a tolerable SD? 12. There have been, rest assured, much calculation to lead  up to that answer. That’s the SD that “doesn’t matter” to accuracy, meaning it’s not going to be the leading factor in a miss. It’s more than I’ll accept for a tournament load, but for those I’m looking for an extreme spread never more than 10 fps (the range might be higher, but now we’re just mincing terms). More later…

The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.

RELOADERS CORNER: Bullet Ballistic Coefficient

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Ballistic coefficient is a term that’s often used but sometimes not fully understood. Keep reading to find out exactly what it is, and what it isn’t…. HERE

nosler rdf
BC is essentially a race between a real bullet and a mathematical bullet. Real bullet never wins… The closer the real bullet gets to the “standard” bullet, though, the higher its BC and the better it’s going to fly. I’d love to get a Kroger-sack full of G1s… Until then, one of these Nosler RDFs will do nicely.

Glen Zediker

A “ballistic coefficient,” or “BC,” is a number that suggests a bullet’s aerodynamic performance.

BC is a component in bullet design that matters much, and it matters more the farther it travels. Bullets that flat out fly, fly flat far out, are of great interest to any longer-range shooter. A bullet with a high(er)-BC is also an advantage at shorter distances, especially when there are variations in the shooting distance. A flatter-shooting (one of the traits supported by a higher BC) bullet means a more flexible zero, a smaller difference in the elevation hold from, say, 100 to 300 yards. BC is influenced by sectional density, bullet weight, and, mostly, its shape or profile.

BCs are derived by comparison. Here’s how that works: There are “standard” bullets that are mathematical models. Bullet designers and ballisticians know which model to apply to different bullet styles. Pistol bullets, for instance, are calculated from (compared to) different models. For the majority of rifle bullets we’ll encounter, one common model is a “G1” (there are others, like G7, which is becoming the popular standard for boat-tail bullets; G1 is based on a flat-base). The flight of this G1 bullet has been calculated at varying velocities and distances. It’s “all math” because a G1 doesn’t exist in a tangible sense.

vld blueprint
Here’s a bullet blueprint. It’s the Bill Davis original 105gr 6mm “VLD” (very low drag). Design factors that influence BC are pretty much every design factor: length, ogive, boat-tail, meplat, weight. All these factors, in this instance, calculate a BC of 0.560. By the way, there’s about a 5 point BC increase for each added 1 grain of bullet weight.

The standard bullet has a BC of 1.000. An actual bullet that’s compared to, for example, the G1 at points, distances downrange, will either be flying faster or slower than the G1 model. If it’s faster, its BC will be greater than 1.000; if it’s slower, it will be less than 1.000. So it’s a percentage of the standard or model bullet’s performance.

Comparing bullets with different BCs, the one with the higher number loses less speed over distance. Losing less speed means its flight time will be shorter and it won’t drift and drop as much as will a bullet with a lower BC. So, a 0.600 flies better than a 0.550.

Depending on the bullet-maker, assigned or published BCs are either calculated or measured. More mathematics than I can wrap my mind around can get these calculations done based on a blueprint. Measured BCs involve chronographing at the muzzle and then at other points on downrange, same bullet, same flight.

Which method — math or measure — provides the best information? Some, and this only “makes sense,” believe that a measured, tested BC is more realistic and, therefore, more valuable. But, if the point is to compare bullets, calculated BCs might be more reliably accurate. I know a number of very serious NRA High Power shooters who have gone to great lengths to “field test” different bullets. It’s not easy to chronograph at long range. Given that information, measured BCs are quite often lower, but not nearly always. Reasons follow.

All the drift and drop tables (whether printed or digital) you’ll see are based on a bullet’s assigned BC. The accuracy of those tables clearly revolves around what the actual, at that moment, BC performance is from the bullet you’re shooting. Also, some bullets have a different stated BC based on muzzle velocity to start.

A whopping lot of things affect the actual, demonstrated BC: anything that can influence bullet flight influences the actual BC performance.

Bullet stability is a factor. For a stated BC to be shown on a shot, the bullet has to be “asleep.” If it’s not stable, it’s encountering disruptions that will slow it down. The rotational speed of a bullet in a test can influence BC. We’ve seen differences comparing different twist-rate barrels, and the faster twists often show a little lower BC outcome.

Atmospherics, which add up as a list of factors, influence BC mightily. Air density is probably the most powerful influence. Any conditions that allow for easier passage of a bullet through the air don’t detract as much from its BC as do any conditions that serve to hinder its flight. BCs are based on sea-level so can easily show as a higher number at a higher elevation.

uniformed meplat
BC uniformity is important to a long-range shooter’s score (less elevation dispersion results). There will be variations in any box of hollowpoint match-style bullets, and a source for variation is the meplat (tip). These variations are the result of the pointing-up process in manufacture. I’ve measured as much as 0.020 inches sorting through a box of 100. A “meplat uniformer” tool eliminates this variance. Uniforming reduces BC 3-4 points, but it’s a trade many serious long-range shooters say is worth the effort. Uniformed on right.

meplat uniformer

Range-realized reality is that the demonstrated BC changes from morning to afternoon and day to day and place to place. The calculated BC is not changing, of course, but the mistake is assuming that a BC is a finite measure of bullet performance. If you’re interested, there’s some valuable information from David Tubb (visit DavidTubb.com). He’s done a volume of work on calculating influences from atmospherics as it applies to his DTR project, which, in one way of seeing it, gets down to understanding why it’s really rare to dial in what a ballistics table says for a particular bullet and speed and distance, and hit the target.

One last (for now) bit of information I’ve always found valuable: a BC is a finite thing in one regard, and that is that any BC derived from a G1 model, for instance, fits all bullets with that same BC. This was helpful before ballistics apps were as common and easy as they are now. For instance, if there was a new .224-caliber bullet with an advertised BC, but no tables, just find another bullet, of any caliber, with that same BC, plug in the velocity, and the drift and drop figures will be accurate.

The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.

RELOADERS CORNER: Bullets 101

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Bullet structure should play an important part in your selections. Here’s a short course in bullet architecture, and why it matters!

224 bullet comparison
There’s probably a wider variety of .224 caliber bullets than any other diameter, and there are whopping differences available! Left is a Hornady 35 V-Max, right is a JLK 90gr VLD. That’s the longest .224 I’ve had to work with.

Glen Zediker

These days we don’t have to settle for much of anything. Pretty much whatever it is, there are options. That’s a good thing, as long as we figure out how to sort through all the options. I didn’t count them all, but there are way on more bullets available now than ever. This article sets out to help you all understand the essential engineering of this all-important ammo component.

The reason there are so many bullets is because there are so many different ultimate uses we put them to.

All bullets are designed or intended to do something, and, clearly, the first idea is to hit a target.

There are bullets engineered to perform variously on target, including the proximity of impacts on target. I say it that way because a “match” bullet’s job is to perforate a piece of paper. A bullet designed for varmint hunting, on the other hand, is designed to produce explosive impact, and one for larger game hunting strives to strike a balance between expansion and penetration. All bullets have to meet their target to be effective, and different premiums often also result in a few trades. Specialty hunting projectiles, for instance, don’t usually out and out group as well as those engineered for target shooting.

However! No matter how it’s built inside, there are universal elements of any bullet design, and those are found on the outside.

bullet parts
Here are the pieces-parts of a bullet. Each element is influential not only in downrange performance, but also in how tolerant or flexible the bullet will be in different rifle chamber and cartridge structures.

Bullet parts: base, that’s the bottom; boat-tail, or not (flat-base); shank, portion of full-caliber diameter; ogive, the sloping “nosecone,”; tip, either open or closed (open it’s called the “meplat”). The shape of the ogive and the first point of “major diameter” are extremely influential elements. The first point of major diameter can vary from barrel brand to barrel brand because it’s the point on the bullet that coincides with land diameter in the barrel — the first point that will actually contact the barrel as the bullet moves forward. When there’s a cartridge sitting in the rifle chamber, the distance or gap between the first point of major diameter and the lands is called “jump,” and, usually, the less there is the better. More in another article.

bullet bearing area
This gives an idea of bearing area. The point that contacts the lands is the first point of “major diameter,” and from there back down the body is what will be in contact with the barrel. Longer area means more tolerant behavior, but lower potential velocity.

The first point of major diameter and the shank combine to determine the bullet “bearing area.” This is how much of the bullet is riding the barrel surfaces. Usually, bullets with greater bearing areas tend to shoot accurately, but, might not get to velocities as high as one with a shorter bearing area. Longer bearing area creates more drag in the bore. Longer bearing area bullets also tend to be more tolerant of jump.

magazine box rounds
This is the round architecture that matters the most to the most of us. We need good on-target performance from cartridges with bullets seated to feed from a box magazine. Choose a tangent profile that’s no more than 8-caliber ogive.

The two essential profiles a bullet can take are “secant” and “tangent.” This refers to the shape of the ogive. A tangent is a more rounded, gradual flow toward the tip, while a secant is a more radical step-in, more like a spike. Secants fly with less resistance, but tangents are more tolerant of jump.

tangert and secant
Tangent, left; secant, right. Tangent ogives are more tolerant of jump, but not quite as aerodynamic at extended distance.

Ogives are measured in “calibers.” That’s pretty simple: an 8-caliber ogive describes an arc that’s 8 times caliber diameter; a 12-caliber is based on a circle that’s 12 times the caliber. The 8 will be a smaller circle than the 12, so, an 8-caliber ogive is more “blunt” or rounded. (So I don’t get comments from engineers, there’s more to it than this, as it applies on blueprints to different profiles; it’s the ratio of its radius to the diameter of the cylinder. But my description is accurate as an overview.)

Bullets with lower-caliber ogives are more tolerant of jump and (usually) shoot better, easier. Higher-caliber ogives fly better, farther. This is an important component in the “high-BC” designs. Same thing comparing tangent and secant: the first is easier, the second beats the air better.

bullets compared
Here’s a good example of the differences in bullets. These are both 75 grains. The one on the left is engineered to be fired from a magazine-length round; the other is engineered to provide better performance over more distance, and it should not be fired at magazine-length. Look at the ogives closely and see the curve difference.

When you see terms like “magazine bullet” or “length-tolerant bullet” that is referring to those with tangent profiles and lower-caliber ogives. (“Length-tolerant” means that it’s not sensitive to seating depth.) If you want to experiment with the longer “high-BC” style bullets, you might find they don’t group well until they get close to or right on the lands when the round is chambered.

More soon…

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The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.