I think it is the action flexes and puts the bolt in a bind with higher intensity loads. What I consider slightly above moderate handloads in the .308 have caused several different Savage 99's to flex and put the bolt in a bind, sometimes making it very difficult to open the action after firing. Once open, the rifle once again functions normally. Zero issues with the same load in a bolt action rifle. This year I am reducing my .308 loads to .300 Savage levels which have never caused an issue in a 99.
I am hoping the 450 Bushmaster does not cause this issue loaded at much lower pressures than the .308.
That's what I think is going on, zero clue if correct.
