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GUNS Magazine June 2010 - Page 8
HANDLOADING • JOHN BARSNESS • ON THE SOFTER SIDE Cartridge case annealing. he past year brought cartridge case shortages many shooters T couldn’t have imagined. For a while some brass was impossible to find, especially .223 Remington. When new brass did start trickling onto the market it cost quite a bit more than prior to 2009. As a result, many shooters who used to reload a rifle case a few times and then toss it are now making every case last as long as possible—and the almost forgotten handloading technique of case annealing is making a comeback. neck ends up harder than the other, so a bullet exiting the neck may tilt slightly. Also, some necks end up softer than others. Neither problem helps accuracy. Proper Technique Some descriptions of this technique suggest tipping the brass into the water is a necessary part of annealing, but the water merely prevents the casehead from Unless we stick way too much powder cases in a pan full of water deep enough being annealed. We want the case head in our loads, expanding primer pockets to cover all but the neck and shoulder to remain relatively hard; otherwise beyond use, the biggest limitation in of the case. The necks were then heated a normal load results in a blown case, case life is the neck cracking due to with a propane torch until they glowed and maybe a blown gun. With brass, airwork-hardening. Many metals become red, then tipped over into the water. One cooling results in the same amount of brittle and crack if “pushed” back and problem with this method is it’s difficult annealing as water-quenching. Also, heating brass really red-hot forth repeatedly, exactly what happens to heat the necks evenly. One side of the can make it too soft. Brass is a to brass after we resize and shoot it “substitutional alloy,” meaning the over and over again. atoms of the two elements have Work-hardening primarily similar structures. Atoms of the affects the neck both because it’s lesser element (in this case zinc) are the thinnest part of the case, and substituted for some of the copper because resizing works the neck atoms. Cartridge brass is about more than the rest of the case. In 70-percent copper and 30-percent typical bottleneck rifle dies the neck zinc. Heating brass hot enough for is first squeezed down when the the neck to appear red in normal brass is shoved into the die, then light requires a temperature above “bumped up” again by the expander zinc’s melting point of 787 degrees ball on its way out of the die. Even Fahrenheit. This won’t melt the when we only squeeze the neck brass, because its overall melting smaller, with bushing or collet dies, Hornady’sannealkit(above)includeseverythingneeded the neck still gets worked more than exceptapropanetorch.Theneckandshoulderofriflebrass point is around 1,700 degrees F, but does make the brass softer than if the rest of the case, especially if we isannealedatthefactoryafterthefinalcaseformingand neck-size only. In time this makes theannealingcanbeseenonthetwoLapua6.5x55caseson heated to just below zinc’s melting point. We want the brass pliable but the neck brittle, whereupon it cracks theleft(below).Ifcasesaren’tannealedeveryfewfirings during resizing or firing, and the theneckeventuallycracks,asitdidontheWinchester.338 not soft. case is useless. Magnumcaseontheright. Workin’ Too Hard It’s also a good idea to anneal the necks and even shoulders of wildcat cartridges after we neck cases up or down or blow the shoulders out. All case-forming techniques workharden brass, something to consider after we’ve spent considerable time creating a batch of .223 Ackley Improved or 6.5-06 cases. Luckily, it’s easy to bring case necks back to life. Many techniques suggested for annealing, however, do almost as much harm as good. For decades the technique usually suggested was to stand the 8 Temperature Brass will anneal at 600 degrees, but it takes an hour at that temperature. Typical annealing instead applies temperatures of around 725 to 750 degrees for a shorter period. The technique I’ve used for the past decade or so was developed by my friend Fred Barker, a retired metallurgist who published an article about it in Precision Shooting magazine. Fred knew the old torch-the-neck technique often resulted in overheating, and also thought it kind of a pain. Instead of a torch, Fred used a simple paraffin candle. Believe it or WWW.GUNSMAGAZINE.COM • JUNE 2010