Tag Archives: full length sizing

RELOADERS CORNER: Neck-Only Case Sizing

Facebooktwittergoogle_pluspinterestyoutube

Neck-only resizing is an option for the bolt-action owner. Here are some ideas on why it works, and when it works best… Keep reading!

winchester bolt action
Neck-only sizing is for bolt-actions ONLY.

Glen Zediker

Cartridge case re-sizing is one of those topics that draws lines and forms camps. I am a big believer in full-length sizing, for any action type or use, and just saying that immediately draws argument.

Before getting into the “whens” and “whys” respecting full-length or neck-only sizing, here’s one that I think is an absolute: cases for reuse in a (any) semi-automatic should be full-length sized; neck-only sizing is only for bolt-actions. Having established that, all this next really only relates to what’s possible with a bolt-gun.

Backing up a bit: a “full-length” sizing die is one that returns the cartridge case body (and shoulder, if adjusted to do so) to near-to-new dimensions. A “neck-only” sizing die doesn’t touch the case body (and may or may not be able to touch the case shoulder). A full-length sizer also sizes the case neck, and, normally, the entire height of the case neck cylinder. A neck-only die can be adjusted to contact the height of the neck cylinder in various amounts.

hornady neck sizer
A neck-only sizing die doesn’t touch the case body, so there’s no reduction in case body diameter. This die can be adjusted to contact the case shoulder, and setting back the shoulder may still be necessary. Make sure you check cartridge case headspace!

The idea behind a neck-only die is to preserve fired case dimensions: make the case a closer mirror of rifle chamber dimensions. One advantage of neck-only sizing comes to those who expect, or need, to get a good many loadings from their cases, since this approach minimizes case stretching on subsequent firings.

However, the primary flag waved by neck-only fans says that it produces the best accuracy, and that full-length sizing is a compromise, favoring function over accuracy. I do and don’t agree, and the rest of this article I hope will clarify what I just said…

The reason I do and don’t agree is that I know folks who cannot get a good group unless they neck-only size, and I know other folks, and I’m one of them, who get very small groups following what many would say is “over-sizing” their cases.

forster neck sizing set
Here’s a nice set for neck-only sizing. The “bump” refers to the capacity to also contact the case shoulder to control its dimension, if wanted.

I believe that the main influence in realizing the virtues of neck-only sizing has a whopping lot to do with the rifle chamber. Specifically, factory-made, off-the-shelf bolt-actions tend to have relatively more generous chamber dimensions, as will many older surplus-sourced rifles. “More generous” is in reference to the tolerances established for the SAAMI blueprint for the cartridge. This is (wisely) done to help ensure that any and all factory ammo will chamber and fire, and also to help ensure general and all-around feeding reliability. Additionally, it’s common to find some (slightly) oval chambers in factory guns; that has a lot to do with the freshness of the tooling when that chamber was cut. It’s even more common to find them that are off-center.

Purpose-built bolt-action competition rifles, such as those constructed for use in NRA High Power Rifle competition, are custom-chambered* and, while few will use what we might call a “tight” chamber, it’s not likely to encounter one on the larger end of acceptable dimensions.
*”Custom,” here, doesn’t mean they are each unique, it just means that they are done by hand employing a precision-made reamer and therefore are what they ought to be, or we sure hope so. And they don’t tend to be overly generous in (any) dimensions.

neck sizing bushings
If you’re going to go, go all in: dies with interchangeable bushings let you control case neck diameter, adding another measure of control, and even less working and re-working of the brass.

So, in the circumstance where we have a chamber that’s a tad amount big and a cartridge case that’s been manufactured to (usually) the smaller end of SAAMI-set standards, that case will endure more expansion, in all directions, than if it had been in a tighter chamber. Sizing only the case neck to accept and retain another bullet, as said, reduces the subsequent expansion that will occur the next firing, but also, and this is likely if there is an accuracy improvement, the otherwise un-sized case might then be sitting more centered in the chamber. And one reason for that is, if the rifle is equipped with a plunger-style ejector (Remington 700 style) that will bear against one edge of the head of the chambered round, pushing the cartridge off-center, askew. (This ultimately creates another undesirable condition, a warp in the case, and we’ll talk about that another time.)

So, a little bigger case returning to a little bigger chamber likely has a little better chance of getting centered, and I truly believe that is why neck-only sizing can be a help to accuracy for a bolt-action. However! A dimensionally-correct case returning to a dimensionally-correct chamber will perform just as well on target. Full-length sizing a case for reuse in a rifle with what I call a “standard” chamber (which is really running a little closer to the minimums established by SAAMI) also makes for good groups. We prove that every High Power Rifle tournament.

Advice: If you notice your bolt-action doesn’t shoot too well with factory loads, neck-only sizing should pay off and is well worth a try. Do, however, make sure to gauge the cases as is often discussed in Reloaders Corner, and, specifically, cartridge case headspace. If the bolt isn’t closing easily, that’s liable to be the culprit right there: shoulder has gotten too tall.

If you’re running a factory bolt-action, by all means try neck-only sizing. If you want to compare results to full-length sizing, just make sure you’re doing that operation right.

david tubb
Now. Don’t go getting the idea that full-length sizing can’t shoot well. Here’s a 1000-yard prone group at the hands of David Tubb, originator of the 6XC cartridge. Tubb sets case shoulders back 0.002 inches, runs 0.004 case neck tension, and full-length resizes using what amounts to a “small-base” die (additional 0.0005-inch reduction at the case head). He’s also not shooting a factory chamber. (Photo note: the yellow pasters were sighters; red pasters indicate record shots).

Check HERE and HERE to get started…

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: Semi-Auto or Bolt-Action? Two Things To Remember

Facebooktwittergoogle_pluspinterestyoutube

There are essential differences in loading for these action-types. It might not matter if you know all about the one, but it is critically important to know about the other. Find out which is which… Keep reading!

casing in air
Any rifle with a gas operation system has to, well, have gas to operate! When it gets excessive is when the problems start. That’s another article, but the effects of the operating system is the basis for both the cautions in this article.

By Glen Zediker

Over the time I’ve been producing Reloaders Corner here at Midsouth, my focus has been exclusively on reloading for rifles, and, within that, primarily for semi-automatics. The reasons for that are based on two things, one is an assumption and the other is plain old fact. First, semi-autos are popular and represent the interest of a great number of new reloaders out there, and that’s my assumption. It doesn’t take long to come to the conclusion that high-capacity magazines and long days at the range combine to get expensive in a hurry! But the biggest reason I focus most of my material toward the needs of the semi-automatic rifle is because there are decidedly important differences in some decisions the handloader makes when tooling up for one. That’s the fact. Not knowing or respecting these differences can be disastrous.

I set out to be a sticker for clarity, but sometimes I overlook making more pointed references to these differences, when there are options associated with any one topic. I judge that based on the feedback I get from you all respecting tooling and component options. I want to start the New Year with this article, which I think contains some basic and important information to always (always) keep in mind. Hopefully it will also reduce questions, and I sure hope confusions. It also seemed to be, judging on feedback, the topic that created the most questions and comments.

Essential: When a round fires, the case expands, in all directions, as much as it can to fit the chamber. Since brass is elastic (can expand and contract) and plastic (can expand and retain that expansion) that last attribute, plasticity, results in a spent case that’s closer to rifle chamber dimensions than it was to its factory-new figures. Since many factory barrels have relatively generous chambers compared to most custom-done barrels, that’s either good or bad, depending on whether it’s a semi- or bolt-gun, and also depending (a lot) on what anyone buys into.

So, for reuse in a semi, that now overly-dimensioned case has to be brought back closer to nearer-to-new condition than it does for a bolt-gun. Has to be. Otherwise it might not chamber smoothly or fully.

full length sizing die
Due to the greater amount of case expasion, and also due to the need for smooth, easy feeding, any and every case used for a semi-auto should be full-length resized.

It’s important to understand that any semi-auto (at least any I’ve yet had experience with) has the cartridge case in a different condition right at the start of the extraction cycle. In a semi, the case is still holding pressure when the bolt starts to unlock. Bolt-gun, it’s all long gone by the time the knob gets lifted. That’s why a freshly spent case from a semi will raise a blister and one from a bolt-gun is cool to the touch. This pressure creates what amounts to greater case expansion in a semi-auto. Depending on the particular rifle and other factors that will get addressed in other articles, this varies from a little to a lot. The spent case measurements from one fired in a semi may not accurately reflect chamber dimensions, as they will with a bolt-gun.

The reason there’s still some pressure within the case when the bolt starts to unlock is because that’s how a gas-operation system functions. If all the pressure was gone the action wouldn’t even open.

neck only case sizing
A bolt-gun can be neck-only sized. I honestly don’t think this is a worthwhile practice, and I’ll talk more about that in another article, but as long as you’re willing to get a handle on case dimensions (so you know it’s still within specs to fit your chamber) it’s perfectly safe, and usually results in good group sizes.

Which brings us to the second essential difference in bolt- and semi-: Most semi-automatics, especially what is probably the most common (AR15 family) is very sensitive to gas port pressure. Gas port pressure is an actual measurement, but that’s not important to know, not really. What matters is understanding the effect of too much port pressure, and that is too much gas getting into the operating system, and getting in too quickly. That creates what most call an “over-function.” The action tries to operate, and the extraction cycle starts too early. There’s a lot of gas still binding the inflated case against the chamber walls. Many ills: excessive case expansion, excessive bolt carrier velocity, extraction failures (extractor either slips off or yanks the case rim, which can come off in a chunk).

.223 recommended components
Semi-autos are way on more sensitive about propellants, and, specifically, the propellant burning rate. Here is the set I use for my .223 Rem. competition loads (aside from a propellent that’s running in the range of the H4895, tough cases and thicker-skinned primers are part of the picture too).

From a reloading perspective, regulating gas port pressure is all in propellant selection. The burning rate range that’s suitable for semi-autos varies with the cartridge, but for both .308 Win. and .223 Rem. I cut it off at the Hodgdon Varget, Alliant RE-15 range: those are fine, but don’t go slower! Bolt guns don’t care about any of that.

RE15
Some will (certainly) disagree, but this is about the slowest-burning propellant I would suggest for .223 Rem. As a bonus, it’s also one of the highest-performing.

THE SHORT COURSE: Think “smaller” and “faster” when tooling up for sizing and choosing propellants for use (really, re-use) in a semi-auto. Smaller case sizing, faster-burning propellants.

This will all be hit on in upcoming articles in far greater detail but…

SEMI-AUTO: full-length case sizing, case shoulder set back at least 0.002 (from what a gage indicates as the fired case dimension), case neck “tension” at least 0.003 (difference between sized case neck outside dimension and loaded case neck outside dimension). Propellant selection: not too slow! Contrary to what logic might suggest, slower-burning propellants produce higher gas port pressures because they “peak” farther down the barrel.

BOLT-GUN: neck-only case sizing is (usually) okay (that means no case body sizing). Case shoulder set back: can be fine-tuned based on what’s necessary to easily close the bolt (ranges from none to “just a tad”). Propellant: doesn’t matter! As long, of course, as it’s suitable for use in that cartridge.

Check out some tools HERE at Midsouth

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: REALLY Understanding Case Neck Sizing

Facebooktwittergoogle_pluspinterestyoutube

Determining and setting the correct case neck diameter is a critical, crucial step in the handloading process: Here’s all you need to know!

sizing die bushing

Glen Zediker

Here’s another I get (too many) questions about, and when I say “too many” that’s not at all a complaint, just a concern… This next hopefully will eliminate any and all confusions about this important step, and decision, in the reloading process.

Basics: A cartridge case neck expands in firing to release the bullet. If the load delivers adequate pressure, it can expand to the full diameter allowed by that portion of the rifle chamber. That diameter depends on the reamer used. After expansion and contraction, the case neck will, no doubt, be a bigger diameter than what it was before being fired.

Back to it: To get a handle on this important dimension, the first step is tools. As always. A caliper that reads to 0.001 inches will suffice.

You need to find three outside diameter numbers: fired case neck diameter, sized case neck diameter, loaded case neck diameter. If you know the loaded case neck diameter then it’s likewise easy to find out the case wall thickness, or at least an average on it if the necks aren’t perfectly uniform (and they won’t likely be unless they’ve been full-on outside case neck turned).

Case neck sizing diagram
“All the math” works in either direction. Here’s how.

A fired case neck has to be sized back down to a dimension that will retain a bullet from unwanted movement (slippage) in the reloaded round. Case neck “tension” isn’t really an accurate term, in my mind, so I prefer to talk about “constriction.” The reason is that making a case neck diameter smaller and smaller does not, after a point, add any additional grip to the bullet. Once it’s gotten beyond maybe 0.005 inches, it’s just increasing the resistance to bullet seating not increasing the amount of tension or retention of the case neck against the bullet. The bullet is resizing the case neck, and probably getting its jacket damaged in the process. If more grip is needed, that’s where crimping comes in…and that’s (literally) another story.

IMPORTANT
Always, always, account for the “spring-back.” That is in the nature of the alloy used to make cases. If brass is sized to a smaller diameter it will spring back plus 0.001 inches bigger than the tool used; if it’s expanded to a bigger diameter, it will spring back (contract) to 0.001 inches smaller than the tool used. This is always true! The exception is that as brass hardens with age, it can spring back a little more.

How much constriction should there be? For a semi-auto, 0.003 is adequate; I recommend 0.004. For a bolt-action, I use and recommend 0.002, and 0.001 usually is adequate unless the rifle is a hard-kicker. See, the main (main) influence of more resistance in bullet seating is to, as mentioned, set up enough gripping tension to prevent unwanted bullet movement. Unwanted movement can come from two main sources: contact and inertia. Contact is if and when the bullet tip meets any resistance in feeding, and gets pushed back. Intertia comes from the operation and cycling of the firearm. If there’s enough force generated via recoil, the bullets in rounds remaining in a magazine can move from flowing forces. However! That also works literally in the other way: in a semi-auto the inertial force transmitted through a round being chambered can set the bullet out: the case stops but the bullet keeps moving. I’ve seen (measured) that happen with AR15s and (even more) AR-10/SR-25s especially when loading the first round in. Put in a loaded magazine, trip the bolt stop, and, wham, all that mass moves forward and slams to a stop. Retract the bolt and out comes a case with no bullet… Or, more usually, out comes a case with the bullet seated out farther (longer overall length). Never, ever, set a constriction level on the lighter side for either of these guns.

Most seem to hold a belief that the lower the case neck constriction the better the accuracy. Can’t prove that by me or mine. If there’s too much constriction, as mentioned, the bullet jacket can be damaged and possibly the bullet slightly resized (depending on its material constitution) and those could cause accuracy hiccups. If it’s a semi-auto and constriction is inadequate, the likewise aforementioned bullet movement forward, which is very unlikely to be consistent, can create accuracy issues, no doubt. My own load tests have shown me that velocities get more consistent at 0.003-0.004 as compared to 0.001-0.002.

Benchrest competitors use virtually zero constriction, but as with each and every thing “they” do, it works only because it’s only possible via the extremely precise machining work done both in rifle chambering and case preparation. It is not, decidedly not, something anyone else can or should attempt even in an off-the-shelf single-shot. As always: I focus here, and in my books, on “the rest of us” when it comes to reloading tool setup and tactics. Folks who have normal rifles and use them in normal ways. And folks who don’t want to have problems.

So, find out what you have right now by determining the three influential diameters talked about at the start of this article. Most factory standard full-length sizing die sets will produce between 0.002 and 0.003 constriction. Getting more is easy: chuck up the expander/decapper stem in an electric drill (I use oiled emery cloth wrapped around a stone), and carefully reduce the expander body diameter by the needed amount, or contact the manufacturer to see about getting an undersized part. I’ve done that.

polish expander
It’s easy to increase case neck constriction if you’re running a conventional sizing die setup that incorporates an expander or sizing button. Just make the button diameter smaller; then it won’t open up the outside-sized case neck as much as it is withdrawn from the die and over the expander.

If you want less constriction than you’re currently getting, about the only way to do that one is hit up a local machinist and get the neck area in the die opened by the desired amount (considering always the 0.001 spring-back). Or get a bushing-style die…

Redding S Die
It’s not perfectly necessary to use an inside case neck expanding tool if you’re using a bushing-style die. I think it’s wise for a multitude of reasons I’ve gone on about in the past, and may should again, but if the math is carefully done, and the cases are all same lot, outside neck reduction will result in consistent inside case neck diameter sizing. Example: Case neck wall thickness is 0.012, outside sized case neck diameter is 0.246 (from using, remember, a 0.245 bushing), then the inside case neck diameter will be 0.222, and that will be a 0.002 amount of bullet constriction (0.224 caliber bullet).

The bushing-style design has removable bushings available in specific diameters. Pick the one you want to suit the brass you use. If you run an inside case neck expanding appliance along with a bushing die, usually a sizing-die-mounted “expander ball” or sizing button, make sure you’re getting at least 0.002 expansion from that device. Example: the (outside) sized case neck diameter should be sufficiently reduced to provide an inside sized case neck diameter at least 0.002 smaller than the diameter of the inside sizing appliance. That’s done as a matter of consistency and correctness that will account for small differences in case neck wall thicknesses. And when you change brass lots and certainly brands, measure again and do the math again! Thicker or thinner case neck walls make a big difference in the size bushing needed.

Check out a few ideas at Midsouth HERE

The preceding was adapted from Glen’s newest book, Top-Grade Ammo, available here at Midsouth. For more information on this book, and others, plus articles and information for download, visit ZedikerPublishing.com