New cases? Decisions you make before that first firing have a lot to do with future success. Read why (and how) HERE

Glen Zediker

case segregate
I segregate my new cases before firing because I need to know which are for which. Do not first-fire cases using a lighter (less pressure) load unless you intend to continue to use that load in those cases for subsequent firings! I’ll use “old” 300- and 600-yard cases for offhand practice, but never the other way around!

The past few articles I’ve been begging indulgence from all the bolt-gunners out there by focusing on a few semi-auto-based topics, and so this time I’ll get to something of more interest to them (and it’s also of interest to “all of us”). In practical terms, which is living with reloads, it is at least of as much interest, or at least importance, to someone running an AR15 (if they’re looking to get maximum on-target performance from it). Subsequent case life has a lot to do with how you go about firing that first time.

So: definition: “Fire-forming” is a term usually associated with describing changing a cartridge from its original or “parent” state into another state, which is a non-standard cartridge, when it’s first-fired in the non-standard chamber. Like making an Ackley-Improved version of a standard cartridge, or converting a .250 Savage into a 6XC. In other words, the firing itself expands and reforms the case to the shape of the new chamber, and the case that emerges is then the new cartridge.

But! All cases are fire-formed to the chamber they’re first-fired in.

Details: Brass alloy is both plastic and elastic. That’s the “technical” reason changes in a fired case can and does occur in the first place. Plastic means that brass can expand and flow to fit the chamber, and retain its new shape. Elastic means that it doesn’t fully and completely mold itself to become a new mirror of the chamber. It “snaps back,” retracts from its maximum expanded form. If it didn’t it wouldn’t want to come back out of the chamber. That “snap-back” amount is predictably 0.001 inches.

case mushroom
Here’s a good example of the plastic property of brass alloy. This is a .250 Savage case that’s been run through a 6XC sizing die. Next step is to load it up and fire it in the 6XC chamber. It comes back out looking just fine! By the way, the little dings and creases we see in spent cases sometimes are really nothing to worry about: they’ll iron out after firing again.

On any rifle with a “standard”-dimension chamber, a new brass cartridge case will be smaller than the chamber. Has to be. It wouldn’t fit if it weren’t. A “standard” chamber, here, means there may and likely will be small variations from chamber to chamber (reamers vary uniquely, as might the operator’s preferences and judgment regarding how “tight” the headspace will be), but nothing intentionally has been done differently to alter the chamber beyond SAAMI-spec dimensional tolerances. Anyone who has loaded for the same cartridge for more than one rifle, and who has recorded pre- and post-fired case dimensions, knows that it’s common for there to be at least a thousandth or two, or more, variance. That’s all fine, as long as it’s within spec. Some custom-done barrels might have a chamber that’s intentionally different than SAAMI blueprints, and that’s a whole different topic.

Back to it: Since the brand-new cartridge case is smaller than the chamber it’s going into, it’s going to expand, grow. That’s clear.

ppc tallboy
Here’s a .22 PPC (left) next to a wildcat version, the “Tallboy.” There’s a whopping lot of permanent stretch to make this round (which is the precursor to 6.5 Grendel by the way). It is really important that this initial firing be done with a stout propellant charge. They would, not may, fail if the first firing didn’t fully expand the shorter PPC case.

So, there are two “forms” fire-forming can take. As said, no matter what else, all cases are formed to the chamber on their first firing. However, for some there can be some benefit from approaching that initial firing following a method or means to establish the set-in behavior of that case on subsequent firings and reloadings.

Here’s why some planning and procedure matters: Brass alloy has a “memory.” This is, more technically, called a “shape-memory effect,” and is shared by some other alloys also. It expands (and contracts) in a consistent pattern each use.

The first firing establishes that pattern. On subsequent firings, less is okay, but more is not. Lemmeesplain: I strongly recommend first-firing with a stout load, or at the least the stoutest load you plan on running through that case in future uses. When I segregate my new cases, I’m sorting them based on their function for me. My best go to the “600-yard” pile, then to 300 and then to short-line. Those are three different loads. I need to know which cases are for which before I make the initial loading. Fire-forming with a lighter load and then using a nearer-to-max load in that same case will, not can, result in premature failures in that case. It doesn’t seem to matter much going the other direction. I would never charge up my 600-yard load in a case formed using my 200-yard load; there are significant pressure differences in those two.

If it’s necessary to reform through firing, making a new cartridge case, there are a few different methods I’ve seen used, but, what really matters is that the case fully forms to the new chamber. The usual influential changes occur in the case neck and shoulder, and also stretching fore and aft. The bigger the change the more important it is to fire initially with a full-power load. For maximum effect, it’s better to fire-form with something closer to a “max” load than something lighter. Brass gets harder each use, less pliable. Starting life as a new cartridge after that first firing, case life is longer, and better, if the case was fully formed.

dead length seating
For maximum subsequent case life, it’s important that, one, a case fully forms to the chamber. But! Two, also that needless stretching is avoided. To that end, first-firing with the bullet seated to touch the lands minimizes stretch. Reduce the load since this will, not may, raise pressure.

To aid that, a “trick” that helps a lot is to seat the bullet into the lands, firmly. The reason is because that already has the base of the case firmly seated against the bolt face. That prevents the primer strike from moving the case forward, resulting then in additional body stretching (beyond what already might be necessary). If it’s not the routine means used for bullet seating, this tactic requires a reduction in the load. When a bullet is moved from “just off” to “just on” the lands, pressure spikes at least equal to the value of 0.2-0.3 grains of propellant.

Glen’s books, Handloading For Competition and Top-Grade Ammo, are available at Midsouth HERE. For more information about other books by Glen, visit


12 thoughts on “RELOADERS CORNER: Fire-forming”

  1. I created 257 Ackley improved brass from 6 mm. I first fire formed them with a little potter charge and cornmeal instead of a bullet. When I first attempted to fire a form them directly to the full-size I had quite a few cases of separation. The finish brass I did worked out fine and is still in use.

  2. Question: Where would you expect failure to take place in a case initially fire formed at a lower pressure? I ask, because I’ve experienced early case failure due to split necks in 257 Ackley cases firefored by the “Cream of Wheat” methoid from 257 Roberts. However, there is very little case neck expansion.

    1. Properly anneal the neck/ shoulder area before the fireforming and every 10 loadings or so to keep it elastic. Use a die that doesn’t overwork the necks. I had a set of RCBS dies that would just eat my brass by undersizing it. Measure a fired brass all over against one that you have resized. If your die is reducing it more than about .002-003″ it will work harden the brass and you will always have low case life. Neck size only if you can. That being said, that cartridge, is a custom fit in your rifle, not necessarily safe to fire in another rifle. Once it splits, it’s scrap.

  3. I have my thoughts on this but would enjoy viewing some more experienced views. Thx for your question I will be following this comment thread.

  4. How you fire form depends a lot on exactly what you’re doing to the case to reform it. If all you’re doing is blowing out the neck to a larger caliber, like going from .30-06 to .35 Whelen, a case full of corn meal over a charge of pistol powder works wonderfully. But if you have move the shoulder forward, change the body taper, and open up the neck, you have to account for head space changes so that you don’t stretch the body in the process.

    Stuffing a bullet into the lands isn’t the best way to do it, especially if the case is larger and runs at higher pressures. Forming a false shoulder at the base of the neck accounts for the head space without increasing pressures. Also, when doing some of the more complex case forming chores, its a good idea to anneal cases before starting the process to make split necks less likely.

    1. Hey Mark, I make ALL my 7 Rem Mag Brass from once fired Federal .300 win Mag brass. You could make your 6.5’s from 7 rem mag or 300 win mag but you would need access to a neck length/ neck turning cutter . (I have a Forster unit that has served me well for over 40 years). Im assuming that you already have dies and reload. I am in Greenville SC and would be happy to show you how to do it, but the sequence of the process is too complicated to note here and somewhat hard to describe if you are not familiar with the process. If you are anywhere nearby and have an interest just reply and we could see if we could meet or at least talk about it. Even email could contain photos and description etc.

  5. When forming 22-250 ACK IMP cases use not only a stout load but a faster burning powder. Lost a few cases with splits running from the neck through the shoulder when I used my “normal” powder.

  6. Be careful there Glen with making recommendations for full power loads for case forming. Cartridge brass will expand perfectly at 30K psi IF you always first ANNEAL the neck/ and shoulder area. (Annealing is easy and fast with simple tools (180- 300 cases per hr). and then take whatever actions necessary to ENSURE you hold the cartridge base securely against the boltface.
    Bullet into lands method, false shoulders on necks, whatever. Just make that happen. ANYTHING other than a condition where primer strike moves case forward in chamber and firing pressure stretches it back setting you up for dangerous web/body separations later. (How I know this is a whole article in itself). Anneal and use starting loads to set headspace and you can feed that case anyway you want later has been my experience. There is a lot of info out there good and bad on this subject available now that was not easy to get to 45 years ago. Get help from a friend who has done it before if you can. Just be careful out there.

  7. Regarding Glen Zediker, here’s a guy that’s been reloading for a “couple of years”,( multiply that by at least 15) . So if he says do this, do it , and if he says DON’T do this, DON’T do it. He has a
    couple of Books in print you should look into. With his wit it makes for good reading and he gets the point across. I started reloading back in the 70’s and am still at it and learning from this Guru. P.S. I hope he don’t read this and come looking for me! Keep yer powder dry.

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