Case Forming

Reloaders Make Their Own Cases For Obscure,
Obsolete Or Scarce Cartridges

By John Barsness

One of the more gratifying aspects of rifle handloading is case forming, especially since some traditional American brass manufacturers are abandoning the production of less-popular cases. While smaller companies usually fill the vacuum, their brass can be hard to find or expensive.

The most common case-forming job is necking up or down. This is normally pretty simple, but there are several potential problems, including cracked necks, collapsed cases or the upper shoulder ending up as part of the neck, creating what’s often called “the dreaded donut,” a ring of thicker brass. If necked down more than a couple hundredths of an inch, necks can also end up too thick overall.

I’ve found it helps considerably to chamfer the case mouth heavily either inside or out, depending on whether the neck is being squeezed down or expanded up. It also helps to use a heavy-duty lube, such as Imperial Sizing Die Wax.

For necking up, more than one company sells long, tapered expander “balls” specifically designed for the job, but standard expander balls can do the job. The egg-shaped balls in Hornady dies work very well. But if you must use standard cylindrical expander balls with little taper, the job would be made easier by first running the neck over an “intermediate” sized ball. As an example, when necking up .308 Winchester cases into .358 Winchesters, first running the necks over an 8mm or .338 ball makes the job more effortless. (This is one reason I rarely sell die. They often come in handy when forming brass for other rounds.)

Cracked necks usually occur when necking up fired brass. Any “working” of brass, whether through firing or sizing, tends to make it brittle, so when necking up used brass, it’s a good idea to anneal the necks beforehand—and often afterwards as well, if necking up more than a couple of hundredths of an inch.

I normally prefer necking brass down, partly because it normally results in straighter necks than necking up. This doesn’t matter after the first firing, but does save range-time and component money. It also avoids the dreaded donut, which can sometimes be thick enough to require removal by inside reaming or very careful outside turning of the neck’s base.

Necking down can also result in all of the neck being too thick. Sometimes this is obvious because loaded rounds won’t chamber, but sometimes it’s just enough to slightly compress the necks around bullets during chambering, resulting in erratic pressures. Making 7mm-08 Remington cases out of common .308 Winchesters normally works fine, but necking .308’s all the way down to a .260 Remington may not work without outside-turning the necks. Overall case length should also be checked after necking down because the neck tends to lengthen as well.


When fire-forming improved cases such as the .22 K-Hornet from the standard Hornet (above),
using a maximum load for the “parent” cartridge works best, filling out the case completely.
There’s no danger using the top-end load because the larger chamber reduces pressures. The
Cream of Wheat (COW) method of fire forming (below) is handy when range-time is limited,
because it can be done indoors. Here a .22-250 case has been transformed into a 6.5
Creedmoor, the fire-forming blowing out both the case body and neck diameter.


The easiest method is to measure the outside neck diameter after seating a bullet. The maximum outside diameter of .260 necks, for instance, is 0.297 inch. If .260 cases made from .308’s measure more than 0.297 with bullets seated, they need to be outside-turned. (A few companies make specialized neck-turning tools, but neck-turning attachments for common case trimmers are normally less expensive, though not quite as precise.)

Collapsed cases most frequently occur when necking brass down, especially cases with tapered bodies, since the die doesn’t support the bodies. Transforming .22 Hornet cases into .17 Hornets is a good example. Both the original wildcat, the .17 K-Hornet necked down, and Hornady’s commercial version, have far less body taper than the .22 Hornet. Since much .22 Hornet brass is very thin, collapsed shoulders are common when necking to .17.

Some .22 Hornet brass is thick enough to resist collapsing, but if you just bought a few hundred rounds of thin brass this isn’t very useful knowledge. As a result, it’s often absolutely necessary to neck down the cases in increments. Luckily, removing the stem from .17 Hornet seating dies can provide a “.20-caliber” neck-sizing die for .22 Hornet brass, and a similar technique can work for other rounds.

Sizing case bodies into a different shape is common, and can normally be accomplished by simply running a well-lubed case into the die. For instance, 7mm Remington Magnum brass is often used to make .257, .270 and 7mm Weatherby Magnum cases. Occasionally, even the case-head can be slightly squeezed down, such as when making a .35 Remington out of a .308 Winchester, as described in the column on the .35 in the September 2015 issue, but requires a stout compound-linkage press and really lubing the case.

Fire forming expands case bodies, the normal method of forming so-called “improved” cases. Usually, this is really simple: just use a maximum load for the standard cartridge and fire away. Since pressure will be lower in the larger chamber, this is perfectly safe.

However, with rimless cases and some belted chambers there’s too much slack—“headspace”—and the expanded cases may partially or completely separate.

This isn’t normally a problem in custom chambers cut in new barrels, because the chamber should be just short enough for a “crush fit” of new brass, but it can be a problem in rechambered barrels. They should be set back one thread before rechambering. Essentially the same problem occurs in many military rifles, because they often have generous chambers to handle dirty ammo.

Seating the bullet out enough to jam firmly into the lands is usually enough to hold the case firmly against the bolt-face, but a starting rather than maximum load should be used, and the bullet must be held firmly in the case neck. Most dies are designed to size necks slightly below bullet diameter, but sometimes that’s not enough to resist the whack of the firing pin, especially in military rifles. Removing the expander ball assembly from sizing dies usually solves the problem, resulting in a neck sized well below bullet diameter. Just make sure to really chamfer the inside of the neck, so cases don’t collapse during seating. (You can also neck up cases, then partially neck them back down again to form a “partial shoulder,” but this means a lot of work, partly because the necks usually must be annealed.)


After necking cases down, say from .308 Winchester to 7mm-08 Remington,
you should check outside neck diameter with a bullet seated to see if it
exceeds specifications—in the 7mm-08, its 0.315-inch.

What’s often called the COW (Cream of Wheat) method can also be used for fire forming. A small charge of fast-burning handgun/shotgun powder is topped by enough uncooked Cream of Wheat to fill the case to the base of the neck, then kept inside by melted wax or some balled-up paper towel.

The COW technique isn’t very useful when simply blowing out case bodies into “improved” cases, because a little trigger time with standard ammo results in plenty of blown-out brass. I’ve fire-formed many cases by prairie dog shooting. But most states don’t have prairie dogs, and near many cities getting to a range is difficult. COW forming can be quietly done indoors by sticking the muzzle against an old catalog, saving real range time for load testing with expanded cases. If it’s even remotely against the law where you live, go to the range.

Unfortunately, no complete manual of COW charges has ever been published. But if you start with a powder charge of 5 percent of case capacity and work up to where cases are completely formed, there’s no danger. I’ve never heard of anybody even blowing a primer while COW-ing. And the filler doesn’t have to be Cream of Wheat. Uncooked cornmeal works too.

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