a rem sendero contour is about the size most use for an accurate hunting gun. the muzzle is about .825. the chamber doesn't really have a straight section and drops down in size very quickly.most order a 1.25 dia for about 2-4 inches then tapers to around .8 at the muzzle.you can get bigger or smaller although i wouldn't recommend anything less than 1.25 for a rem action.most have a preferred or limit in weight for a gun and that controls what size barrel they get.
where do you live,i'm down below chambersburg