As far as separating headstamps, I do kinda' take an effort when dealing with revolver/rifle rounds and 30-30 rounds, but I really don't (normally) pay attention to the bottom feeder rounds I load - which are only 9mm and .45 auto. A year or so ago, I picked up a small batch of "AMERC" brass in .45 auto, cleaned it and just tossed it into my bulk stash. I ended up loading a few of them in my normal mixed brass sessions last year and they randomly got mixed into boxes of reloads. At the range one day I had a f-to-f and just cocked the hammer and tried again to no avail. Then, racked the round out with a primer-less round and a nasty mess of powder in my old Kimber. I managed to clean it up and get back to shooting and didn't think much about it until a couple of months ago when the exact thing happened again. Both times were AMERC brass. After doing a bit of web searching I discovered that AMERC wasn't a favorite among re-loaders (I'm being polite, which is difficult for me). I did go through every box of my stash of .45 auto re-loads and pulled out a dozen or so AMERC brass loads (and parted them out) ... and made myself a note to carefully sort out any AMERC brass for the recycle bag when I load .45 auto.
My old .45 Kimber Compact is more a PITA to field strip/re-assemble than a Ruger Mark XX .22 pistol, so having to deal with that at the amusement park ain't fun. No more AMERC brass for me ... yep, I check head stamps.
jd
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