I'm attempting to sight in my grandfathers Rem 721 30-06 and having some issues. Admittedly I don't claim to be anything more than a novice at best, so we'll start there. That being said I've successfully sighted in my .17 HMR, .243 and .223 to a satisfactory level ~ 3"/3 shot groups at 100 yds. Problem is, the 30-06 just will not shoot consistently accurate at 100 yds. I'd say the pattern is aprox 6 - 9" in 3 shot groups. One shot may be decent (within 3" of target) but the other two are 6-9" outside...mostly high and right. I've switched scopes and get the exact same inconsistent results. I have not switched rounds yet but can that really make enough of a difference to matter? I've been using 180 grain Winchester ammo up until now btw. I don't think it is the gun, but dont know for sure? I know my grandfather successfully hunted this riffle in AK for Moose, bear, deer and Caribou for years. Right now I'm researching barrell heat effects but there does not seem to be a consensis opinion that this would have a large effect at 100 yards to the degree I am experiencing. I'm at a loss. Any suggestions? Do I need a new riffle? It is in great condition and has always been stored inside with the greatest of care.