Any time you change ammunition it can and usually does make a difference in group size and point of impact.

If Remington Core Lokts are giving you 2" groups then try Winchester power points (silver box) orFederal power shock (blue box). If these still don't shoot well then move up to more expensive ammo like Hornady innerlocks or SST's.

Generally speaking, the more simply constructed the bullet is the more potentially accurate it will be.