Case Sizing 1: Sizing Die Selection

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The following is a specially-adapted excerpt from the forthcoming book,” Top-Grade Ammo,” by author Glen Zediker, owner of Zediker Publishing. Click here to order.

by Glen Zediker

Most discussions about reloading tend to center around tools, and the cartridge case–sizing die used to refurbish a spent case is one of the most important. Last time, we were left with a case that had been expanded to the limits of the chamber, plus maybe just a little. The sizing die gets it back in shape for a reuse.

First, I only advise the use of a full-length sizing die for bolt guns or semi-autos. As suggested, a full-length die contacts the full length of the case, the full diameter, from case mouth to case head, and can also contact the shoulder area. There are neck-only dies that, as suggested, only resize the case neck so it will hold another bullet. They don’t touch the case body, and many don’t contact the case shoulder.

As far as brands go, I’m partial to Forster. I like the expander design. It’s located high, so there’s more support about the case when the neck is withdrawn back over it. I still polish this appliance, and recommend always doing so if it’s possible.
As far as brands go, I’m partial to Forster. I like the expander design. It’s located high, so there’s more support about the case when the neck is withdrawn back over it. I still polish this appliance, and recommend always doing so if it’s possible.

A full-length sizer will compress the case body down to the die interior dimensions, which are close to those of factory new ammo. Keep in mind that we’re talking about scant thousandths of inches, but those add up.

Whether it’s a bolt-action, lever-action, semi-automatic, a rifle has to function, and ensuring that cartridges feed into and out of the chamber is the clearly most critical functioning necessity.

If you’re big into or only into single-shots, neck-only sizing is possible, certainly. But even then there’s honestly little to no accuracy or performance benefit from it. The idea is that maintaining the case-body dimensions that more closely replicate the rifle chamber generally tightens up everything and produces better accuracy. Makes sense. But unless we’re working with measurably perfected brass and perfectly concentric rounds and seating bullets to touch the lands or rifling, none of those attributes matter a whit. Any rifle with an ejector is going to warp case bodies, for instance, so the dream of case-to-chamber harmony just can’t exist.

This is a Redding Type-S conventional full-length sizing die. On these, the die interior is pretty much the same as the rifle chamber interior, just a little smaller.
This is a Redding Type-S conventional full-length sizing die. On these, the die interior is pretty much the same as the rifle chamber interior, just a little smaller.

If neck-only sizing was all that influential, then new cases wouldn’t shoot the good groups that they will.

Another thing a full-length sizing die does, or can do, is contact the case shoulder. This is critically important in sizing for repeating rifles.

Last time we talked about what happens to a cartridge case during firing, and it’s not pretty. One of the things that happens is that the case shoulder gets blown forward, which means that if the case were standing up on the bench, that the shoulder will be higher (taller) than it was before firing. To ensure function, and safe function, that dimension needs to be corralled and brought back to what it should be.

To polish the expander, chuck the stem (lightly) in a drill and use a wrap of masking tape to cushion the threads. I first run the edges of the expander over a hard stone to break them and smooth them over, but I don’t run the stone against the body of the expander. Then run it over wet 600-grit emery paper. I use emery paper available at many auto-parts stores. Aluminum-oxide lapping compound works well also. There should be no measurable reduction in the expander body diameter after using the 600-grit paper, but if there is, it’s not going to amount to anything that can have a harmful effect.
To polish the expander, chuck the stem (lightly) in a drill and use a wrap of masking tape to cushion the threads. I first run the edges of the expander over a hard stone to break them and smooth them over, but I don’t run the stone against the body of the expander. Then run it over wet 600-grit emery paper. I use emery paper available at many auto-parts stores. Aluminum-oxide lapping compound works well also. There should be no measurable reduction in the expander body diameter after using the 600-grit paper, but if there is, it’s not going to amount to anything that can have a harmful effect.

There are full-length sizing dies with interchangeable bushings that size the case neck. The idea is to control the amount of case neck reduction, and it also allows the use of a sizing die without an inside-neck sizing appliance (usually called an expander). Good idea. Still, I don’t recommend this style of die for most shooters. One reason why is that there’s a small amount of case neck that doesn’t get sized. Over time, this can create or increase the “case neck donut,” the small raised-up ring of brass that exists inside the case at the case-neck/ case-shoulder juncture. But the die is not the sole cause. Suffice it to say, the additional and inconsistent additional constriction against the bullet isn’t a good thing.

I also do not advocate running a sizing die without an expander or sizing button to control the case neck inside diameter (i.d.). That’s another touted advantage of the bushing dies. That only works well if case necks are perfectly uniform in thickness. Otherwise, it creates off-center case mouths, and ultimately, inconsistency, in bullet pull.

Neck-bushing-style dies (in conjunction with full-length sizing die body) seem like a really good idea, and they can be — but they are another step in controlling case dimensions that most of us don’t want to take or need to take. My biggest issue with bushing dies is that they don’t size the full length of the case neck, and that can create problems. The arrow points to the small area of the case neck that is sized.
Neck-bushing-style dies (in conjunction with full-length sizing die body) seem like a really good idea, and they can be — but they are another step in controlling case dimensions that most of us don’t want to take or need to take. My biggest issue with bushing dies is that they don’t size the full length of the case neck, and that can create problems. The arrow points to the small area of the case neck that is sized.

One of the reasons that the neck-bushing dies came about was from the warranted complaints that conventional sizing dies sized down the case neck outside too much. Most do. Then the expander or sizing button has to open it back up that much more. That’s a lot of stress on the case and the reason for polishing the expander. Another easy fix is to have a machinist open up the neck area in the die. That’s a good idea. I can’t get after the factory techs too much in setting the specs for their dies because they’re trying to cover their bases on all the potential combinations out there, but that doesn’t mean we can’t improve it. There doesn’t have to be more than 0.005 difference between outside diameters and inside diameters to ensure fully adequate sizing. In other words, if the case O.D. is sized down to 0.005 smaller than the measured O.D. after the expander has passed back through, that’s plenty. Check your die by sizing a case without the expander in place. Less is better, but don’t cut it too close; keep room to account for different brass brands, which have different wall thicknesses. This trick will help maintain more material consistency over the life of a case. Otherwise, it’s like bending a piece of metal back and forth until it breaks; the same effect does influence case life when there’s excessive material movement.

One of the best ideas in sizing dies is incorporating a neck-shoulder bushing. These work well because they allow for control over dimensions, including case-shoulder compression, and without the criticisms made against neck bushings. This is a set from Superior Shooting Systems LLC. It’s for 6XC but can also be used, with an appropriate bushing, for .308 Win. Full-length dies with neck/shoulder bushings can control the neck diameter and still get the full neck cylinder sized.
One of the best ideas in sizing dies is incorporating a neck-shoulder bushing. These work well because they allow for control over dimensions, including case-shoulder compression, and without the criticisms made against neck bushings. This is a set from Superior Shooting Systems LLC. It’s for 6XC but can also be used, with an appropriate bushing, for .308 Win. Full-length dies with neck/shoulder bushings can control the neck diameter and still get the full neck cylinder sized.

A small-base full-length sizing die is an option in some die makers’ catalogs. As implied, this reduces the lower portion of the case a tad amount more. I’ve never encountered the need for one in an AR-15. Most have fairly generous chambers, especially if it’s a true NATO-spec. However, I always use one in my M1As, especially when working with a tough case, like a Lake City, that has to fit back into a relatively undersized match chamber. One of the best I’ve used is from Dillon (just the standard die that comes on the Blue machines); Redding also makes a “National Match” sizer engineered just for that rifle.

Next time, I’ll go step-by-step on how to set up a sizing die.

Get looking around this website and locate a cartridge headspace gage, and get it bought. I’ll show you how to use it next time. Either the Hornady LNL Cartridge Headspace Gage or the Forster Datum Dial (shown here) is my recommendation. They both work well. There are also drop-in style gages that will suffice to keep your ammo safe, but won’t give a number to work from.
Get looking around this website and locate a cartridge headspace gage, and get it bought. I’ll show you how to use it next time. Either the Hornady LNL Cartridge Headspace Gage or the Forster Datum Dial (shown here) is my recommendation. They both work well. There are also drop-in style gages that will suffice to keep your ammo safe, but won’t give a number to work from.

 

 

 

 

 

 

 

 

 

 

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17 thoughts on “Case Sizing 1: Sizing Die Selection”

  1. I’m sorry, I have to partially disagree. I have a 220 Swift that refuses to shoot new brass or brass that has been full length sized. Neck sizing is the only way to go with this rifle, cases get fired 6 or more times before there is even the slightest stretching. This is the gun that made it necessary to become a reloader 26 years ago. The head space is touching the lands and grooves, and eliminates a lot of barrel wear. After all these years it still shoots groups at 200 yds. you can cover with a dime.

    1. You are all correct, but I respectfully disagree. The primary focus of this department is to help newcomers create good ammunition for use in semi-automatic rifles. Certainly, neck-only sizing is possible and some think wise in a bolt action, especially one that’s fired more or less as a single-shot (like a varmint rifle). However, and for example, for use in competition across-the-course bolt rifles, full-length case sizing is wise. Nobody wants a sticky bolt. Minimal sizing does extend brass life, but, again, when smooth function is important, a little more case sizing is necessary. I usually trash cases way before head separations, etc., because I’m not willing to do all the repairs they need to keep going, and I freely admit that. Things like annealing, neck reaming, and so on are just too tedious for me because I’m loading high volumes of ammo.

  2. My experience has been some what contrary to the Author’s. I have a Cooper 54 varmiter in 6.5×47 lapua. Factory ammo grouped at 1.42 in. with h the 123’s and 1.35in with the 139s at 100yrds from sand bags. Hand loads using Reloader 15 and ne k sized only cases with Seirra 140’s group at .365 at 100 and .768 inch at 300 yards. These are 5 shot groups. As a side I only clean the barrel when the groups open up beyond an inch which is around 100 rounds or so. This may be due to the fact that I have “tuned” this load for the rifle or that it just prefers my load to Lapua’s. But regardless I have 19 reloads on my original 20 pieces of brass, neck sizing the top 5mm of the neck only, each reloading. I anneal every 5th loading and use a body only die to set back the shoulder on the 5th reloading as well. I admit that this method will not work with Autoloaders. But I am a man of meager means and neck sizing preserves my rather pricey cases and allows me to get the oat out of my brass.

  3. I have been reloading for 25 yrs. and have also shot competitively. I am in total disagreement with this authors assumptions on neck sizing. Although neck sizing is not recommended for every type of action, where applicable, it DOES improve accuracy and extends case life.

    1. Larry

      I too disagree. I have been reloading 55 years, for at least 30 different calibers. Until I discovered neck sizing, or in some cases partial sizing, I lost many cases to separation. In several of my rifles I form the cases to the chamber before ever shooting a round at a target. One of the best and least expensive neck sizer comes from Lee. You can even adjust your bullet pull by the amount you polish the mandrel.

  4. I don’t see the problem with neck sizing only. For my bolt guns, that’s all I do. Haven’t had a single issue, but I don’t have any brass that has been loaded more than twice yet. Eventually (if I ever get that many firings out of them), I may have to bump the shoulder back a bit. I like the neck sizing because I don’t need to lube the cases.
    I test every round I will use for hunting to make sure it feeds from the magazine and the bolt closes easily. So, for me, I’ll stick with neck sizing only, mainly because I can skip the lube and, maybe I’ll get more loads from the brass.

  5. I agree with you Alan. Neck sizing only is a sure way to tighten the groups and manufacture consistent loads for a specific bolt gun. Besides, neck sizing only a fired case is a sure way to avoid the repeated “shoulder blown forward” dilemma that full length sizing the case causes during each firing, shortening the life of the brass due to premature shoulder and neck failure.

    Apparently the author does not or chooses not to utilize neck concentricity, neck turning, and neck wall thickness tooling, among other tools available.

    And what is this about sitting the projectile on the lands. Talk about an unnecessary pressure bump to get the projectile on the move. If you sit on the lands, reduce the powder charge to avoid the higher than usual initial pressure spike.

    1. I very frequently do a lot of case segregation and case prep for my long-range loads. Neck turning, etc. etc. and all that helps. Setting up a full-length sizing die correctly doesn’t significantly add to the case shoulder movement forward. Use a gage and keep it minimal. Case shoulder contact creates sticky function in a bolt-action, and, after the chamber gets dirty, can interfere with bolt locking in a semi-auto. The next article here is all about cartridge case headspace in setting up a sizing die.

      Seating a bullet to touch the lands or rifling when the round is chambered is a pretty common, pretty well accepted tactic for target shooting. It does spike pressure! Back of AT LEAST a half grain of propellant before trying this. Some of the more extreme secant-style bullets don’t want to shoot well unless they’re resting on the lands, and that’s why any more I prefer tangent ogive competition bullets.

      1. Offering new reloaders generalized loads and missing information begets marginal success, which will lead to failure. Failure is discouraging. I stated that I partially disagreed. Semi auto and bolt guns differ but marginally, even neck sizing can be utilized in semi auto platforms, but then that comes with experience. Being meticulously accurate comes from repetition. Mass loading leaves too many loose ends and also leads to failure on so many levels. If the end product can only hit an elephant in the rear, by all means, full length size everything.

      2. I’m sorry Glen, I went on a little tangent. The gun that got me started reloading was a Ruger M77 markII 220 Swift stainless heavy barrel. It was a consignment in a local gun shop. A friend of mine had one and it was extremely accurate, so when I saw this rifle, almost brand new, I had to have it. I bought 5 boxes of Hornady Custom and brought it home. I placed the same scope on it as my friends. A 6.5×20 Leupold vari-3. At 100 yards, an elephant was safe. I was sick. I asked my friend what was up with the inaccuracies. He informed me that I had just became a reloader, if I wanted to keep it. This rifle, since 1992 will not shoot new brass, manufactured loads of any brand. I bought a press and lots of brass, it was still a bargain at gun shows back then. I started with my friends recommended load, to no avail. So after becoming discouraged, I queried him for more details. Neck sizng was his answer. After doing some research, neck sizing wasn’t the total solution. The Swift at the time of its inception was a barrel burner. The sheer speed of the round wore out barrels. If you increase the head space to be in contact with the lands, there is no running go and sudden torque that wears out the rifling. I still shoot this rifle with extreme accuracy. 52 grain bthp match, cci bench rest primer and H380 powder. The only thing that makes my load similar to my now deceased friends rifle is the neck sizing and the head space. I have used it on many calibers with great success. Sorry again about the tirade. A fellow reloader. Thanks for all you do to advance the sport.

        1. I hope to help folks understand more about some important topics in handloading. The next one that will run is all about cartridge case headspace, which, without a doubt, reflects right back on case sizing. I kind of have to cover things one at a time, and also move from general to more specific. In giving advice to someone I don’t know, I have to stay general. After time, and experience (hopefully most of it good) we learn how to deal with specific circumstances that might stray from the “starting point” advice. So. This department, at least over the next few segments, is geared to making as few mistakes as possible in reloading ammo that will work in most everyone’s rifle. Safety is always the primary concern. Keep in mind also that my competitive shooting background is primarily NRA High Power Rifle, not Benchrest or F-Class. There’s a lot of primer-popping, case-eating semi-autos in that game! Everybody tries to get the max velocity from the .223 with 80 and heavier bullets, and cases sustain some damage as a result. I do treat long-range bolt-gun loading differently. I get good accuracy from my routine across-the-course loads, that are fully sized: I expect about 4 inches at 600 yards in my AR15-platform race-guns. A bolt-gun will do better, to be sure, but with a group at 1/3 the 10 ring size, there’s enough margin, technically, to shoot an easy clean. I hope after reading the next piece on headspace and how to control it, folks might also understand better when more or less sizing is warranted. Thanks for reading these articles, and taking the time to participate with me in doing them.

  6. Great informative article, that explains the two major methods
    of resizing, and in plain language which is best for shooters
    intended purpose of the hand loaders use..

  7. Very interesting article. I have read it 3 times. The third time I read it, I also read all of the comments. VERY cool stuff guys. I’ve been handloading for about 15 years. In my travels, I did a test, and then found a similar test over on chuckhawks.com where rounds were loaded in different batches. Every batch had one variable tweeked. The chuckhawk test as well as my own test lead me to believe that neck sizing , (and flash hole de-burring), leade to a far more accurate round. HOWEVER, I do agree with Mr. Zediker about fl sizing for autos, especially when there is more on the line than small groups, (think Texas hog hunting), and that autoloader must function flawlessly. I am eagerly awaiting the next installment!

  8. I own two Pro Hunter barrels 28 inch, 30 caliber,and 243 I found just neck sizeing alone wasn’t working
    I had problems with ejections out of the chamber had to take a pic to get shell out when resizing the whole shell I had no problems. And as far as accuracy there wasn’t any difference. Also just neck sizing the 30 caliber case I had two cases that would not even enter the chamber the cases i used where Hornady match new out of the box.

    the chamber the barrel, the 30 cal Hornady match cases where knew.

    1. I think Glen’s articles and books help all levels of reloaders. They are great for the beginner and advanced, because they make you think and for me experiment which has me shooting more.
      Thanks
      Bob Delaney

  9. I have done numerous studies using a FL die with integral button type neck expander (ALL carefully set up, mind you – that is another topic), and found the results to be inferior to: FL die w/o expander button, followed by expansion treatment with a Lyman “M series die to open the neck sufficiently for a bullet to be easily seated.

    The differences in neck and bullet runout were startling, to say the least. This is the technique _I always use_ when not employing a sizing die with a resizing doughnut.

    These studies were always performed doing the conventional resizing with the typical neck expanding button on the stem, measuring the results, and then repeating the process with the stem button removed, opening the neck with the “M” series die.

    The results were spectacularly different. I used the same set of brass for each study, doing the “button” resize first, and the “no button – Lyman ‘M series’ second.

    And, when are you going to tell the masses about Redding’s shellholders which, while permitting COMPLETE contact of the die to the shell holder, allow variations in headspace from +0.002″ to +0.010” on the sized case.

    Mic Macpherson (or, “Mick MacPherson, or, Mic McPherson; get it? ) wrote an excellent article in Precision Shooting, which I cannot locate at this moment, regarding these “competition shellholder sets”- all in black and white and easy to understand why we need this set of tools. I believe the article was entitled “What Happens To A Case?”

    The short story is that when one runs the FL die UP to give more optimal headspace, the die is no longer hitting the shellholder, and as a result of this, inconsistent resizing WILL occur due to differences in brass hardness, consistency of lubrication, ad nauseum.

    With the Redding solution, your die will always bottom out at the shellholder, giving confidence that the sizing is consistent.
    Ive’ tested these things, and _they FREAKIN’ WORK!

    Redding has really missed the boat here on educating the public as to how superior this system is.

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