Sounds like you need to have the headspace checked. Sounds like the chamber could have been bored a couple thousandths too short. Probably just needs a quick chamber cleanup. Most factory-cut chambers are far from perfect. You could always go ahead an have the chamber cleaned up (bored) with a .270 Ackley Improved reamer instead of a regular .270 Win. Better chance of getting a good shooting chamber if you clean it up with an AI reamer, as it removed as much of the factory chamber as possible to allow you to cut a true, straight, and properly-spec'd chamber. Probably won't cost you any extra to have done, but you gain some velocity from the added capacity.