I bought a Diamondback AR pistol in 300 Blackout. 10.5 inch barrel. I took it out last week and shot sub-sonic 220 grain. I had two failure to feed issues, but I expected some teething issues. Today I ran some Hornady practice ammo, 125 grain BTHP. Advertised velocity 2175 fps from a 16" test barrel. I was really curious to see what it was from a 10.5" barrel. A bit surprised when I came up with 2111 average. About 11.6 fps per inch. Not bad. No issues.
I bought 1K once fired brass, various head stamps. I loaded up a ladder of 150 grain Hornady HPBTs over Accurate 1680. First string looked good, 19.4 grains 1803 ave 6.5 std dev. Up .2 grains, second shot of the string, I get lined up squeeze off the shot and CLICK no BOOM. Failure to go into battery. That sucker was stuck. I thought crap, I should have crimped, I set one back. So that was it, it wasn't coming out. I extracted the round when I got home figuring I was going to see a set back bullet but no. The neck on that piece of brass was really thick. I didn't resize this brass, just chamfered and loaded. I don't think sizing would have made any difference. I checked length but not neck thickness. I had one that was a btch to seat though, and when I checked it I saw the neck was all shiny from being so tight in the seater die. Should have checked them all. I'm going to have to go through all this brass. Some bargain. I also need to get a go-no-go gauge. From what Ive read, this once fired brass began life as 5.56. Don't know if that's true but it makes sense because length varied considerably.
I kind of rambled here, but I thought I'd put this info out there for anyone who's interested.
