i have a remington ADL synthetic in 243 that does basicly the same thing except i get away with two shots then grouping expands.with mine its pure barrel heat.its that 22 inch sporter barrel,it is not intended for rapid firing.when at the range,working up a new load i give the barrel a minamum of 10 min in the shade between shots.after cleaning mine i always shoot several fouling shots.it will only group good after fouling.