by Bmt85 » Wed Sep 12, 2018 3:42 pm
If I had to guess, it’s from the carbine length gas system on the 20” barrel or case not sealing properly (as Hoot mentioned), or both. As long as your not seeing signs from unlocking early, I wouldn’t worry about it. As far as cases sealing properly, if you have a bunch of soot on the outside of the case, you might want to up the charge a little. I prefer to run loads that properly seal, but again, you don’t have to worry about it a whole lot, because most factory ammo I have shot (I don’t shoot factory ammo now, because I reload) doesn’t completely seal. In my opinion, running slightly over book is fine because it should have less bolt thrust than a mid book load that doesn’t seal. Just a FYI, I’m the only one that I know of that has broken a bolt, but that bolt came from a company who has known issues with Grendel bolts, and the 450B is thinned out even more. I ran a pretty heavy load on that one, yet I have 3 other bolts that I’ve beat on harder and for longer, without issue. So I wouldn’t worry about upping it a bit if needed.