Ron, I've only re-barreled one 6XC so far - a PacNor 3-groove 8-twist on a customer's rifle. He's the kind of shooter who would be at least as hard on a barrel as a 1000yd. BR shooter - except he doesn't clean barrels nearly as often. It's not unusual for him to sit and shoot up a couple of 50rd. boxes of ammo at steel targets from 600-1000yds., with not a whole lot of time allowed to let the barrel cool between shots. He was using N560 & mostly DTAC 115s (moly'd), and put at least (according to him) 3300rds. through it before "accuracy kinda fell off". After I borescoped it, I could see why - there wasn't any sign of lands for well over an inch ahead of the chamber.