Suddenly my 10mm brass has insufficient neck tension. After resizing (i.e., before use of the expander die), the bullet can sometimes even be seated by hand, with no use of the press required! Obviously, setback happens too easily, so I've disassembled all the rounds exhibiting this characteristic. I'm using PPU-marked brass that's been fired at least once, and probably 2-3 times before, all at loads well below book max and with no exhibition of pressure signs.
I measured the bullets (Montana Gold JPH's), and they are right at .400; some Berry's that I had were just a touch larger on average, but I got the same neck-tension problems with them, so I don't think it's an undersize batch of bullets.
Any idea what's causing this? Has the mouth of the case been work-hardened so that it's springing back despite the resizing die? Has the brass gotten too thin (I haven't trimmed); PPU seems to be a touch thinner on average than the Starline that I use for stronger loads. Can resizing dies go out-of-spec or get loosened in some way after about 1000 rounds? Any suggestions are appreciated.
I measured the bullets (Montana Gold JPH's), and they are right at .400; some Berry's that I had were just a touch larger on average, but I got the same neck-tension problems with them, so I don't think it's an undersize batch of bullets.
Any idea what's causing this? Has the mouth of the case been work-hardened so that it's springing back despite the resizing die? Has the brass gotten too thin (I haven't trimmed); PPU seems to be a touch thinner on average than the Starline that I use for stronger loads. Can resizing dies go out-of-spec or get loosened in some way after about 1000 rounds? Any suggestions are appreciated.