I am wanting to build a custom XP 100. I am only going to use it for varmints. coyotes,crows bobcats. Would a improved 6BR gain any advantage over a 6BR or would it be better to just get a 15 or 16 inch barrel instead of 14 inch 6BR. I have a XP 100R in 22-250 now. Wanted to shoot to 300 yds or more.