Only down side was the barrel heated up faster than usual and the groups opened up to just under an inch. Cool down the barrel and they seemed to tighten up a bit but not as tight as a clean barrel.
You might want to recheck your bedding. When a rifle changes POI (groups opening up) when the barrel warms up, there might be a stress issue. If the action was bedded with any stress in it (like happens when action screws are tightened while the bedding epoxy cures) that can definitely show up as the rifle heats up.
A little tip. After you shoot a few rounds on a cold barrel, feel the barrel and see where it seems hottest. If hot all the way to the muzzle, your choice of powder is too slow. Ideally the last third of the barrel should be noticeably cooler than the first two thirds. This indicates that you have a powder that burns completely within the barrel and pressure peaks have occurred BEFORE the bullet leaves the muzzle.
You can actually "see" this phenomena if you have one of those relatively inexpensive I/R Thermometers. Take readings every 6" on a barrel after you've shot 5-6 rounds from "Cold".
FWIW, the A-Max not only has a higher BC, they also tend to travel faster due to the shorter bearing surface (secant ogive gives longer bullet with shorter bearing surface). In fact the design has been "kicking Sierra's butt" enough that Sierra has now introduced their "Tipped Match King" (TMK) design. Still more expensive though.
