GUNS Magazine May 2013 Digital Edition - Page 12

fiRefoRMing BRass an iMporTanT Technique for a handloader To learn. artridge brass is about 70-percent copper and 30-percent zinc, a relatively low-cost alloy that’s easily softened (annealed) by heating or hardened by “working” to enhance certain characteristics. The relatively thick head of the case is left work-hardened after manufacturing to contain pressures, but the front end of the case is annealed to remain more flexible. This flexibility helps the neck hold a bullet firmly, and also allows the thin walls of the case to expand during firing, sealing the chamber against gas blowback, then contract slightly after pressure drops to allow extraction. This flexibility also allows rifle addicts to create new cartridges. If the rifle’s chamber is reamed larger, the brass case will expand to fit the new chamber. This fireforming is usually connected with wildcat rounds, with steeper shoulder angles and less-tapered bodies capable of holding more powder. But blowing-out brass has also created new factory rounds: The .300 Weatherby Magnum is an improved version of the .300 Holland & Holland, and Nosler recently legitimized the .280 Ackley Improved, a popular wildcat (see February 2013 issue free at www. gunsmagazine.com/digital-editions). Sometimes fireforming can also be used to turn cheaper factory cases into other factory cases that might be scarce or expensive, so any avid handloader should be familiar with various fireforming techniques, as well as potential problems. The biggest problem is maintaining headspace. A slight amount of excess headspace results in case stretching, or even separation near the case’s head. Rimmed and belted brass can be fired without any worries, but the firing pin can drive rimless brass a little too far into the new chamber, shortening the headto-shoulder distance. Most rifles re-barreled to improved rimless cases have the chamber set up for a slight crush-fit with factory brass. New cases have a slight radius between the neck and shoulder, just 12 C John Barsness full-pressure handloads in new brass, and the improved cases will come from the chamber perfectly formed. Many handloaders, however, are tempted to save money by using reduced loads to fireform cases, often combined with cheaper cast bullets. But if pressure isn’t near the SAAMI maximum for the parent round, the case heads might not be driven back firmly into the bolt face, and some cases can still end up with a slight amount of excess headspace, even with a crush-fit chamber. Unless you plan to segregate cases for use with reduced loads and/ or cast bullets, fireform with a fullpower load using jacketed bullets. Since we’re handloaders anyway, most of us will fire handloaded new brass, and a maximum load for the parent case will guarantee complete expansion of the improved case. new BraSS BeSt It’s not absolutely necessary to use new brass, but it works best for a couple of reasons. First, firing workhardens brass, especially the thinner body and neck. If the brass has been fired more than once or maybe twice, it can crack during fireforming. (Work-hardening is also why it’s a good idea to anneal brass after fireforming, since the extra stretching to fill the new chamber walls work-hardens brass even more than normal firing.) Second, when new rimless brass is fired the first time in standard chambers, it loses that slight radius between neck and shoulder, so doesn’t headspace as firmly when chambered in a crush-fit improved chamber. As a result, case stretching or even misfires can result. I once went on a prairie dog shoot with a friend who brought a brandnew custom rifle chambered for an improved cartridge. This is a really good way to fireform a bunch of brass, but about every fifth round from Joe’s new rifle wouldn’t go bang. He started cussing the gunsmith, but I interrupted the blue streak to ask if his handloads were in fired brass. They were—and once he got back home and switched to new brass the misfires disappeared. Misfires also tend to occur when an improved chamber isn’t reamed for a new-brass crush-fit. This often happens when somebody runs an improved reamer into the chamber enough to help maintain this crushfit against the firing pin’s blow. If your rifle’s set up this way, all you have to do is fire factory ammo or The most enjoyable way to fireform a bunch of brass is prairie dog shooting (above). Rimless cases like the .35 Whelen (below, left) need to either firmly “crush-fit” in an improved chamber, or have the bullet seated out to firmly meet the rifling to properly fireform. Rimmed or belted brass can simply be chambered and fired, as Roy Weatherby did when transforming the .300 H&H into the .300 Weatherby Magnum (right). W W W . G U N S M A G A Z I N E . C O M • M AY 2 0 1 3

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