Question: Rex, still confused on what heating up the barrel does to affect accuracy. Is it because when it is heated up molecules can move more freely therefore making the barrel less rigid? Thanks for any help!
Rex: Its not really a rigidity issue... Most folks think 'heat warp' is the main concern - however, its effects on POI are usually not practically significant. A more common issue in my experience is that a heated barrel will heat up the ammo, which will often results in powder burn rate changes that can significantly increase muzzle velocities. This will affect both bullet drop as well as potentially change exactly where (within the vibratory pattern of the barrel) the projectile exits the muzzle, changing POI. There are also changes in the bore / bullet's relationship in lubricity as temperature changes, but these effects are usually very small as well. Lots more detail on all this in the coming videos :-)