Thanks, Barney. I was wondering where the information was coming from. However, I understand that both the AMU and the Marines were using extremely hot loads for an M-14 in order for the bullets to remain supersonic and stable at 1000 yards. The high pressure loads may have more to do with the op-rod damage than the bullet weight. The reason I was using 175 SMK's was that they shot so well in my rifle while the lighter bullets didn't. I took your advise to try the 155 Hornady A-Max with my 175 match load. Now I have a light bullet load that shoots the same as the 175's. Thanks for the information. Steve