Originally Posted by Natty Bumpo
I've never owned or shot an A-Bolt, but I've heard they have thin barrels. Maybe if you give the barrel more time to cool between shots your groups will tighten up a little. I wouldn't worry too much about standard deviations. The load with the tightest velocity range won't necessarily be the one that shoots best in your rifle.
I agree with the first part of your post but couldn't disagree more with the last part. If long range shooting is the goal, one must pay attention to the standard deviation of the load to avoid big vertical dispersions in group at distance. In fact, if using some of the longer range bullets that have long lengths, they may not shoot super tight groups at close range but if the standard deviations are low, they can shoot amazingly good groups at longer range.
Btw, standard deviations would have very, very little to do with the mechanics of the rifle. Standard deviations deal with combustion and pressure among other internal ballistic properties. To get low Sd's, the brass must be uniform, have equal neck tension, and have deburred flashholes. Then the powder must be consistently charged, the primers seated same, and the bullets must be seated uniformly to maintain equal distance from the riflings. And even after all that had been done, the standard deviations can still be large if the wrong amount and/or the wrong powder was chosen. To fix it, go up in charge .5 grains until it improves. If it never improves, then switch to a different powder and try again. This should yield some load that has good sd's.