While choosing your bullet is important, your cartridge cases also deserve attention. There are lots of reasons to trim cartridge cases, but by far the most common reason is because bottlenecked rifle brass stretches when it is fired. If you don’t keep your fired brass in spec, you can experience some very unpleasant results. The long case can keep the bolt from fully closing and locking. The best you can expect from over-length brass is that you will experience failures to function and failures to fire. At worst, you could have a catastrophic failure if you manage to force the end of the brass into the barrel beyond the chamber.
I’m speaking from experience. A couple of years ago I had to rebarrel an M1 Carbine because pressure spikes caused by out-of-spec brass on some offshore factory-loaded ammunition cracked the gas cylinder.
For most of my life, I’ve used a Lyman hand-cranked, bench-mounted trimmer for that chore, but Lyman has a much more convenient system for the more common rifle calibers. Lyman’s E-Zee trim system is a hand-held trimming system that uses case-specific pilots to guarantee foolproof case trimming. The system consists of a trimmer body that holds the cartridge case securely, a cutter head and a set of steel pilot guides for five popular rifle cartridges: .223, .243, .270, .308 and .30-06. All you supply, besides the fired brass, is the shell holder—the same shell holder you use for the cartridge on your reloading press.
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All you do is install the appropriate pilot into the trimmer head, lock a piece of brass and its shell holder in the trimmer body, and insert the guide into the cartridge case until the cutter head is contacting the case mouth. Turn the cutter head by hand, cutting down the brass until the pilot bottoms out inside the case. You can’t trim too far because the pilot stops you at the correct case length. And, if you want to save the elbow grease, the system comes with an adaptor to mount the cutting head on a power drill. Trimming cases doesn’t get much easier than this.
For more information, visit http://www.lymanproducts.com or call 800-225-9629.