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Posted: 9/30/2016 6:39:27 PM EDT
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I've been reloading for almost a year now. Yeehaw!
Each time I re-use 223 and 308 brass, I trim and chamfer the case. My guess is each time I do that, and resize the case, the neck walls are getting thinner due to the trimming/chamfering. Is this correct? And also the reason the neck will eventually crack/fail after too much use? I'm not sure how many uses I can get out of a case since bits of brass are being removed each time. Also, I see posts about neck sizing and concentricity, but is that only necessary for precision shooting? Not really necessary for AR plinking (or even bolt guns for that matter)? I pretty much just resize in the resizing die on my LNL press and go. Thanks. |
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Trimming and chamfer have no select on neck splitting.
How hot your loads are and work hardening is what makes them brittle. Annealing the next is what helps stop them from getting too hard and brittle. If your excessively trimming after each load you are over sizing the case and the case is stretching upon firings. Push back the shoulder no more than three thousandths of an inch will be fine for autoloaders. |
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You don't want to chamfer until you have a sharp knife edge. Really don't need to chamfer fired brass unless you trim the cases and then only to remove the sharp edge left by the trimmer. Most don't trim and chamfer pistol
cases unless you're loading cases like .357 Magnum-44 Magnum or other rounds that need a good roll crimp. If these pistol cases have varying lengths then trimming to a certain length will give you more consistent roll crimps. Reason why most necks could split is simply the brass gets work-hardened from firing and resizing. Like bending a wire multiple times until it breaks. Necks probably get just a bit thicker after multiple firings as the brass expands forward also making it grow in length and needing trimming. I really like the Very Low Drag VLD deburr tools for rifle case chamfering. It has a better cutter angle and cleans up the inside neck better and prevents the neck from scratching or shaving the copper off the bullets. Even on fired brass that don't need trimming I do very lightly turn the case mouth deburr tool to feel for burrs or knicks but not to remove more material. Just feeling for knicks or burrs. |
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Chamfering should actually be nothing more than what we call a corner break in the machining world. Like the last post stated you don't want to end up with a knife edge case mouth.
Having a knife edge case mouth can make splitting occur more easily but neck splits are typically caused by the brass becoming brittle. Motor |
You question has been almost answered. If you want max life from your cases (neck don't crack) you need to anneal them. |
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