How to Form Brass Cases for the Frugal Reloader

Once a new wildcat cartridge design becomes popular—but before it is adopted and legitimized by a big ammo company—shooters form cases for it by shortening and/or necking up or necking down readily available parent cases. A classic example would be necking up the .30-06 to make .35 Whelen cases.

Eventually, the most popular wildcat cartridges get SAAMI approved and become factory rounds. But even then some shooters prefer to form cases out of some other cartridge—either due to lack of supply or cost. My old shooting mentor had thousands of once-fired .30-06 Lake City Match cases, and he made everything from .25-06 cases to .35 Whelen Improved cases from them.

Whatever the reason, a basic understanding of how to form cases for your favorite cartridge out of something else is a fundamental skill that every serious handloader should have.

Before making any large changes in a cartridge case’s shape, it’s necessary to make sure it’s clean, and that the brass is not brittle. Brittle cases are stubborn to form into other shapes, and a lot of cases are lost to cracked necks or caved-in shoulders.

Clean Cases

Cleaning cases is easy: Simply tumble them in a traditional tumbler with walnut-hull or some other common media. Remedying brittle brass is more complex, and because the required annealing process is fairly complicated, I’ll leave that for another time. If you’re already familiar with it and you’re using old, tired cases, do anneal them before running them into your case-forming dies.

I typically use once-fired brass from factory-loaded ammunition. That ensures it hasn’t been work-hardened, and it won’t have been overpressured.

If you are forming cases that are shorter than the parent case, trim them nearly—but not quite—to the eventual overall length before forming. There’s no need to shape extra brass that’ll just get cut off anyway after the fact.

The easiest of all case-forming operations is a simple neck-up or neck-down. The .25 Creedmoor cases I’ve been creating recently are about as easy as it gets. Because the shoulder angle and datum points from base to shoulder angles are the same as the 6.5 Creedmoor, I just lube 6.5 Creedmoor cases and run them into a match-grade 6.5 Creedmoor die fitted with a .25-caliber neck-size bushing. It’s as simple as that.

Necking Down

If reducing a case neck diameter a larger amount—for example when sizing .30-06 brass down to make .25-06 cases—it’s best to form it in increments. In this case you’d bump them down to 7mm/.284, then 6.5mm/.264, then to .257 diameter.

At this point, you may or may not be about done. Small changes don’t thicken brass necks much, but a large change—such as from .308 down to .257 inside diameter—may thicken case neck walls so much they’ll need to be thinned by neck turning before being used. I’ll cover this shortly.

Moving the shoulder on a case back a significant amount is a bit tricky. Be sure case shoulders are well-lubed but not over-lubed. Go slow and accept the fact that you’ll likely lose some cases to collapsed walls or shoulders or whatnot.

The most I’ve done is for an 8x60 Mauser German sporting rifle, creating brass from the .30-06. Here, the cases must be shortened, shoulders moved back, and necks bumped up in diameter.

Procedures

Here’s how I go about it. After trimming .30-06 case length about 0.13 inch, I remove the 8mm expander ball from my sizing die and carefully bump the .30-06’s shoulder back to the correct spot.

At this point there’s a step in the new case’s neck where the rear part of the neck is formed down to 8mm, with the shoulder in a new, shorter location—but the front .02 or so of the neck is still .30 caliber. I then reinstall the expander ball, lube the inside of the case necks with a bit of aerosol-driven grease, and size the necks up from .308 to .323 inside diameter.

At this point there’s also a slight bump in neck thickness partway up the neck. I use a neck-turn tool to remove this bump, and again, I’ll cover that process in a bit.

A simple increase in internal diameter is even more simple than sizing necks down. You may lose a few cases to cracking, but you never have to neck-turn sized-up case necks because they don’t thicken; they thin.

Make Sure To Lube

For this you’ll want to use quality dies with smooth-surfaced expander balls, and I’ve found that RCBS dies generally work well. It’s necessary to lube the insides of the case necks with a premium lube.

As when sizing down, a small step is easy—like sizing 6mm Creedmoor cases up to .25 Creedmoor. If you’re making necks significantly larger, take it in steps. All you’ve got to have is a series of expander balls. For example, if you’re making .35 Whelen cases out of .30-06, first bump the necks up to 8mm/.323, then to .338, then finally to .358 inside diameter.

What if you want a cartridge with the shoulder farther out than it is on the parent case? This requires fire-forming.

Belted magnum cartridge cases are easy because the belt holds the case in place while you fire-form it. For example, you can shoot .375 H&H cartridges in a .375 Wby. Mag. chamber. The belt holds the cartridge in place while the firing process stretches the case to seal the chamber. When you open the action, out comes a freshly minted .375 Wby. Mag. case.

Jam The Lands

Non-belted cases are harder. To hold the cartridge rearward against the bolt face, you’ve got to “jam the lands.” Seat your handloaded bullets just a whisker long, so when they chamber they’re forced to engrave slightly into the rifling leade. This will keep the cartridge case firmly rearward as it fires. It sounds extreme, but is a common method of creating new cartridge case shapes.

Once the fundamental shaping of your formed cases is done, you’ll need to trim each to precise length, then deburr the outside of the case mouth and chamfer the inside of the case mouth with a low-drag chamfer tool.

As I’ve mentioned, forming cases into new shapes can cause a lot of brass to flow and mold into new positions. When sizing up, case necks tend to shorten. A few firings will cause the brass to stretch and flow, and eventually they’ll be the correct, SAAMI-specified overall case length.

However, even though they’re starting life short, they need trimming. Why? To make them all the same length and to square up the case mouths, both of which are crucial to accuracy.

Trim to Length

When sizing down, cases usually grow, meaning they get longer. These definitely need to be trimmed to length, or they may not fit fully into your chamber. They too need to be trimmed to a consistent length and squared up.

In most cases, you’ll be done after forming and trimming the parent case. However, any time there’s a significant compression to a smaller diameter, case necks will thicken. Similarly, any time a case shoulder is moved rearward, there will be a step in thickness in the neck area.

These newly formed cases will need to be neck-turned to reduce neck wall thickness and to level any steps in thickness out of the neck. Neck-turning can be done with a hand tool, but it’s much more efficient and usually more consistent to use a powered neck-turn.

Case forming can be as simple as churning out mass quantities via a simple neck-down step or as complex as completely reshaping a parent case through fire-forming. When carefully done, the result is the same: gleaming new cases formed into exactly the shape you need.

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