That's strange. I've put some of my 30 & 35 grain loads through it and get horrific groups, the same rounds going through the bolt gun are touchers. I've ruled out bbl length, the AR is 16, the bolt is 18, IMO 2" isn't going to change much. If anything the AR barrel is heavier than the bolt barrel. The only thing it cold be is the twist, my handloads for the AR are in the 3200fps realm with a 55gr bullet, my handloads for the bolt gun are a little beyond the red level for pressure/velocity at 4050fps which is why I was going for the twist rate. The bullets are so small I can't discern keyholing just bad groups. And before anyone comments about the reloads, I worked up to them and have no case damage or ejection issues, they slide right out of the chamber. In fact I can rechamber a piece or fired brass with no problem.