Tag Archives: precision reloading

RELOADERS CORNER: Learning to Load Again, pt. two

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In handloading, there’s always another gage or means to measure. But which really matter, and when and why? READ MORE

reloading measuring tools
All you really need. And a few gages to index it off of. Read on!

Glen Zediker

Last time I started on a recollection of a recent event, which was a project (that is ongoing) teaching my son Charlie how to reload ammunition for his AR15.

As said then, learning to set up tooling is intertwined with learning to measure pertinent dimensions, and that experience involves learning to use measuring tools, and choosing which ones to use. That led to a look at the most essential and indispensable measuring tool of all: the caliper.

There’s more tools to be had, and to be used, to be sure.

As he was looking through my boxed and binned collection of tools I had fetched out for the project, he had a lot of “what’s that’s” and “when do we need this’s” and I kept telling him what it was, what it did, and that we didn’t really need it for what we were doing.

Most of that other stuff was measuring tools, very specialized measuring tools, gages. A commonly recommended tool for a handloader’s kit is a micrometer. These use a threaded barrel that’s turned in to a stop to measure the thickness or length of something (any lateral measurement). A “mic” is a more precise tool than a caliper, usually reading down another step, into the 0.0001 inches range.

reloading measuring tools
If you get a micrometer, digital is a lot easier to use, but I really don’t think you NEED a micrometer!

A mic is useful for measuring bullet diameters, for instance, or sizing die expander buttons. A specialized mic, called an inside or tubing micrometer, is the most precise way to measure case wall thicknesses. These have a ball end to more accurately mate with the curved shape of a case neck.

As with calipers, mics can be either manual or digital. Digital is a whopping lot easier to read, mostly faster to read, because there’s another layer of graduations to count toward an answer, in effect, on the barrel of a manual mic. No shock, a good mic usually costs more than an equally good caliper.

I can’t count too high recollecting the times I’ve used my mic in handloading. I use it more building rifles, measuring trigger pin diameters and the like.

reloading measuring tools
Something like this Forster tool can perform valuable quality checks. Here it’s being used to measure case neck wall thickness.

For me, the more useful means to check and note neck wall thicknesses (probably the most commonly applied use of a micrometer by in-depth handloaders) is a specialty gage that works off a dial indicator. These have a ball-end like an inside mic. Then the quality of the dial indicator matters a whopping lot. Good ones are expensive, but, in my experience, worth it. Take extreme careful care of your dial indicator!

reloading measuring tools
Something like this neck wall thickness gage from Hornady is not as perfectly precise as a tubing mic, but sho is faster to use. It all depends on how ticky anyone wants to get.

That measuring device, the dial indicator, is the heart of a few other measurement fixtures I’ve used, like a concentricity fixture to check the runout of cases or loaded rounds. One of these “spinners” is a good investment for someone who wants to get a little farther along toward perfecting ammunition, or at least being able to segregate it. The expense isn’t great, and the collected and applied results can be most beneficial. Most of these also provide a means to configure the appliance to check and record neck wall or case wall thicknesses. The accuracy is, as suggested, dependent on the quality of the dial indicator. Since most indicators have a “standard” 1/4-in. diameter shank, it’s usually possible to ramp up a fixture to incorporate a higher-precision dial if wanted.

reloading measuring tools
A good dial indicator makes the most of any tool based on one.

I have owned and used a good number of seriously specialized measurement tools. I unfortunately can’t say they ever really helped, or at least they didn’t help me for the targets I was facing. Long range and Benchrest shooters tend to be behind the development and production of tools such as bullet bearing surface comparators. As anticipated, this contraption actually measures and compares bearing surface area bullet to bullet. As with a more common caliper-mounted comparator, the idea is to measure through a box of bullets and segregate them into batches. The idea is that the bullets that are more nearly the same will perform more nearly the same on target. Whether those efforts are going to manifest in a smaller group is a combination of ammunition component quality to start, rifle component quality, and, no doubt, shooter skill.

reloading measuring tools
Here’s a bullet bearing surface comparator, the most specialized such device I have. Such measuring tools come about from attempting to attain near perfection. Most of us, shooting most guns at most targets, won’t see any difference.

I’ve known folks to check bullets using an electromagnetic appliance to gauge concentricity and, some think, much more respecting the internal structure and balance of each bullet measured. If you’ve never seen or heard of one, check out a Vern Juenke Bullet Inspector. Some say voodoo, some say magic. I can’t say I saw any difference.

reloading measuring tools
Here’s a Juenke. There’s still no verdict on exactly what it is that it does, but some swear by it!

So, meandering back to the point of this: all these different measuring tools and appliances do have specific points and places in handloading. These points and places can and have been, and no doubt will again be topics for specific articles.

Beyond that good caliper, though, there’s a very short list of measuring tools I will recommend as “must haves.” Top of that list is a cartridge headspace gage (which is used with that caliper). That’s beyond wise. Beyond that, a good concentricity fixture with a decent dial indicator might actually give some feedback that will improve a group for the most of us. Another is a bullet comparator, useful for those who want to do seating depth experiments, along with a gage to determine the distance to the lands in the barrel.

However, it is possible to load x-ring ammo without ever operating a micrometer. Promise!

Check out Forster spinner HERE 

Check out neck wall thickness gage  HERE 

Check out micrometers HERE 

The preceding is a adapted from information contained in from Glen’s books Top-Grade Ammo and Handloading For Competition. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

 

 

RELOADERS CORNER: Understanding Ballistic Coefficient

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Math and myth both get involved in bullet Ballistic Coefficient discussions. Keep reading to separate the two and learn exactly what BC is, and what it isn’t. MORE

bc

Glen Zediker

Years ago I explained in great detail to a fellow here all about ballistic coefficient and how it was calculated and how it could be used and how it can change and so on, and he stopped me: “So you mean it’ll hit furtherer on up the hill…” That’s it.

A “ballistic coefficient,” or “BC,” is a number assigned to a bullet that suggests its aerodynamic performance.

That’s a key word, “suggests.” The main suggestion is how well this bullet will fly compared to that bullet, and the one with the higher BC ought to fly better. Fly better means less drop and drift, and those, factually, are a product of the higher-number BC. My best all-inclusive definition what a higher BC does for us: less speed lost over distance. Regardless of the muzzle velocity or the distance, one bullet with a higher BC will lose relatively less velocity over the same distance.

bullet blueprint
Here’s a blueprint. All the information needed to calculate a BC is contained here. It doesn’t have to be a real bullet because a BC model is not a real bullet either. Design factors that influence BC are virtually every design factor: length, ogive, boat-tail, meplat, weight. These factors, in this instance, calculate to a G1 BC of 0.560. By the way, there’s about a 5 point BC increase for each added 1 grain of bullet weight.

BC is calculated based on a standard bullet model. There are 7 of those. Two are normally used to determine BC for conventional rifle bullets, like what the most of us reading this use. Ballisticians and designers know which model to apply to different bullet types. The common model is a “G1” (another is 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 does not in fact exist. BCs are derived by comparison.

g1
The older standard for most rifle bullets was the G1. The newer, and better, standard is the G7. However! BC is never chiseled into stone regardless of the model. It’s a way to compare bullets, and a place to start figuring yours out.

g1 and g7

The standard bullet of any form-factor has a BC of 1.000. An actual bullet that’s compared to the model at points downrange will either be flying faster or slower than the model. If it’s moving faster, its BC will be greater than 1.000. If it’s going slower, it will be less than 1.000. It’s a percentage of the standard or model bullet’s performance.

Now. That is also all that it is!

BC is not an infallible factual statement about precisely what a bullet will be doing when it’s loaded and fired at that target than moment with that rifle. Not nearly, not hardly.

To me, BC gives us a place to start estimating drop (elevation) and also clues to how much it will get moved by a wind. It’s a way to compare bullets.

BC changes! Day to day, place to place, hour to hour.

Some bullet makers publish a BC for a bullet based on actual testing (chronographs) but now it’s pretty much “just math.” That’s fine. Which — math or measure — provides the best information? Some believe that a measured, tested BC is more realistic and, therefore, more valuable. But, if the point is to compare bullets, calculated BCs is more reliably accurate.

We (NRA High Power Rifle shooters) have gone to difficult and frustrating lengths to collect data to calculate “real” BCs (chronographing at 500+ yards hain’t always easy). Measured BCs are quite often lower, and they are quite often higher. Reasons follow.

The accuracy of drift and drop tables clearly revolves around what the actual, at that moment, BC performance is from the bullet you’re shooting (compared to what it’s “supposed” to be).

Anything that can influence bullet flight influences the actual, demonstrated BC performance.

BC uniformity is important. Bullets that show uniform BC performance produce less elevation dispersion. A source for variation is the meplat (bullet tip). Hollowpoint match bullets are notorious for inconsistency in this area. There’s a tool, a “meplat uniformer,” that fixes it. That’s pretty much the point to the plastic points on bullets like Hornady’s A-Max line.

Atmospherics, which add up as a list of factors, have a huge influence on BC performance. 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 stated BC as do any conditions that serve to disrupt its headway. BCs are based on sea-level so can easily show as a higher number at a higher elevation. I can tell you that bullets fired at The Whittington Center in New Mexico have a noticeably better BC than those shot at Port Clinton, Ohio.

Range 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.

Bullet stability is even 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 tested BC.

Factors that don’t matter in BC? Caliber. I’ve been argued at often over this next, but it is perfectly and absolutely true: BCs work the same regardless of caliber or bullet weight. Two bullets that each have a 0.550 BC, for instance, behave the same. That’s helpful, and at one time was more helpful than it is now. When we had to use paper tables to get drift and drop data and there was a new bullet that didn’t yet have those tables done, all you had to do was find data for another bullet with the same BC, go to the same muzzle velocity, and that data was 100-percent accurate. A .308 and .224 that both have the same BC share the same table. Remember, it’s not “real,” it’s a mathematical model.

So if you take a load to the target one day and you’re putting on more elevation than the BC-based calculation says you should, the BC isn’t wrong. The day is just different.

Finally, does it matter (really) if a bullet BC is based on a G1 or G7 model? Debates continue. But, not really, and I say that because BC is still only a suggestion. G7 is a more closely matched model to what we’re usually shooting when we think of a “high-BC” bullet, but all the same factors day to day also influence its accuracy. Given access to the data, I definitely, though, go with G7 calculations to have a place to start from. My experience has been that there is less difference in varying conditions, but, again, it’s still (plenty) enough change that you cannot dial it in and win anything…

The preceding is a specially-adapted excerpt from Glen’s book Handloading For Competition. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

RELOADERS CORNER: Throwed Vs. Weighed

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This is an age-old debate among precision reloaders, and here’s to hoping you can find your own answer. Here’s a few ideas on how…

Glen Zediker

Since we (well, I), have been on the topic of velocity consistencies, clearly, this next here factors mightily among points in this general topic. I would also very much appreciate feedback on your own experiences. This, therefore, isn’t so much me trying to convince anyone of anything, but rather an effort to give some credibility to “both sides” of this question. The question, as suggested by the article title: Are meter-dispensed propellant charges equal in performance to singly-weighed charges?

Most are going to own a powder meter. Technical tickiness (that’s actually important): such a device is a meter, not a “measure.” Meters don’t measure. It’s most accurately called a “dispenser.” That’s what it really does. The “measure” is comparing a meter drum volume to a weight on a scale. It’s a volume, not a weight. The volume corresponds to a weight that was arrived at through adjusting the meter volume.

And this kind of keeps going in circles: is it a weight or a volume, then, that matters? A good many chemistry-inclined folks have told me over a good many years that any and all chemical measures are always weight, never volume.

harrells
I think a truly good meter is necessary to provide reliable results, especially if you want to ignore weighing each charge and rely on thrown charges for your record rounds. There are good meters available, but this is one of the best: Harrell’s Precision. It uses the proven Culver-style mechanism. See one HERE

Now then there’s a question about adjusting volume for that weight. I don’t know if you’ve ever experimented with this, but I’ve weighed the “same” powder charge at different times and had different weights (storing it in a sealed film canister and weighing on different days). It’s not much, but it’s different. It pretty much has to be moisture content that’s changing the reading, and, most lab-standard dispensing recipes (such as used in pharmaceuticals) have a set of condition-standards that accompany compound weight. Compounding that, using some electronic scales, I’ve had to re-zero, more than once, in a loading session weighing out charges. I have an inherent suspicion of scales. Old-trusty beam scales with a magnetic damper can finish a little high or low due only to the magnetic device. There’s a certain amount of inertia the beam has to overcome. Tapping the beam a few times will show that, indeed, it can come to rest variously +/- 0.10 grains, or more.

I don’t have a definitive answer to this question!

I can safely say that “it depends,” and what it depends on is a long list. First, as suggested, is scale accuracy. I don’t know that it’s always all about money, but that, no doubt, is a leading contributor in product quality. As said, I become suspicious of any device that requires a re-set during one use-session. For myself, I have confidence in my meter, and that’s come from countless “quality checks” I’ve run over the past couple of decades. I’m not a mathematician, so perhaps those who are can tell me if my logic is flawed in making the next assumption, but I developed confidence in metering charges based on collectively weighing multiple charges. Like so: throw 10 into a scale pan, weigh it. Repeat, repeat, repeat, and make note of how much plus-minus there is in each try. Using the propellant I stick to for competition NRA High Power Rifle loads (Hodgdon 4895) I get never more than 0.2 grains variance for a 10-throw batch. I don’t know how many single throws might be more or less than that and maybe it’s pure luck that all unseen errors offset rather than compound, but I prefer, at least, to believe that means my meter throws pretty well.

reloading scale
A truly good scale is likewise important if you’re going to rely on weighing each charge. If not, then just about any scale is accurate enough to set a powder meter. Speed factors heavily in being happy with a constantly-used scale.
trickler
You’ll need one of these too! A powder trickler. It’s used to drop in one kernel at a time to perfect the weight on the scale.

That’s for me. A different propellant, different meter, different scale, might all mean a different way of thinking, a different method to follow. So, to be most clear: I am not saying not to weigh each charge, and I am not saying not to trust a meter. Let your chronograph and on-target results give you the best answer for your needs. This debate is probably as close to a religion as exists in reloading (well, along with full-length case sizing and neck-only case sizing). And most of the answer is plainly anticipated: if you’re throwing large-granule stick propellant (especially large amounts per charge), you might better ought to weigh them out, but if you’re throwing a small-grained stick propellant, a good meter might actually prove more accurate, given any questions about scale accuracy. Spherical propellant? Weighing that is truly a waste of time.

The point to this, beyond bringing up a topic for input-discussion, is to find some way to settle such questions for yourself. For me, and likely for you, the ultimate answer is founded in the confidence we can have in whichever is the primary dispensing apparatus: the scale or the meter.

[Ballistician and Olympic Shooter, Ken Johnson, shares his thoughts on this topic in his piece on Precision propellant.]

Check out Midsouth offerings HERE and HERE

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