I have a H&R .308 and been having a problem with it. The breech will not stay closed after firing a round! I sent it back to H&R for repair and they said it was fixed, think again, went to the range today and after two rounds the breech came open again, not alot, but enough to stop shooting. I was wondering if the round I am using is too much? I am using Hornady 150gr Super Performance rounds. I was wondering if this could be the problem Any ideas?