Annealing Methods for Rifle Cases
If you reload your own ammunition, you will eventually need to anneal your cases. An ammunition case is made of brass, and houses the powder, primer and the bullet itself. Repeated cycles of firing and reloading the brass cases causes the brass to undergo a process known as "work-hardening," whereby brass becomes hard and brittle under repeated stresses. This can lead to the case splitting when fired---a dangerous situation. Annealing is the process of heating the brass to about 650-700 degrees Fahrenheit, then letting it cool. This softens the metal just enough to keep it from splitting.
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Annealing Machines
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The best way to anneal large numbers of cases is to use an annealing machine. This is usually a wheel that holds a number of cases and rotates them past a propane torch just fast enough to let them reach the proper temperature. The cases then cool on the rest of the trip around the wheel and drop out into a holding basket, ready to go. Ken Light Manufacturing sells an excellent annealing machine designed for home set-up and use. The slight downside to using an annealing machine is since you must adjust it to heat each case to the correct temperature, you may ruin a few cases before you get it set up properly. However, once set up properly, an annealing machine can handle as many cases as you feed it, and will do it consistently and correctly.
Hand Annealing by Color Change
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If you don't want to spend the money for an annealing machine, you can anneal your cases by hand with a propane torch. One way to do this is by observing the color change of the brass as it is heated. In a dark room, a brass case will just begin to turn a dull red when it reaches the correct temperature for annealing. When it reaches this point, the heat is removed and the case is allowed to cool. Cases can either air cool or be dropped in water; the speed of cooling will not affect the annealing process. A word of warning: Do not heat any part of the case besides the neck (top area that holds the bullet). Doing so can cause a case to rupture when fired, possibly damaging your firearm or causing injury to yourself. Annealing a case using color change to indicate temperature can be tricky, because observing the color change is a subjective process that takes some practice. This is not the best method to anneal cases, but will work with practice.
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Hand Annealing with Temperature Sticks
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Another method for hand annealing cases is to use a temperature stick. Temperature sticks are crayons that melt or change color at a specified temperature. Marking the case neck with a 660 degree Fahrenheit temperature stick and then heating the case neck evenly with a propane torch is the preferred method of hand annealing. The temperature stick mark will let you know exactly when the case reaches the proper temperature, then the heat is removed and the case allowed to cool. Temperature sticks can be purchased from various sources, including Tempil and McMaster-Carr.
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- Photo Credit 3 5.56 ammunition- vary side view image by Yanir Taflev from Fotolia.com
