The lighter the barrel, the sooner heat will cause groups to open up, bull barrels are less prone to this, Superlights are more prone, specially with the hotter cartridges like the 243, the 22 Hornet is far less subject to larger groups caused by barrel heat than a 243 or even the 223. For a big game rifle, it's real simple, since only one round is normally used, I only shoot two shot groups with the light barrels, seldom are two shots ever needed if the first shot is well placed. For a colony shooting round for varmints some forend work like full bedding or pillar bedding may be required.
Tim