I have a 270 in a Ruger M77 and a Sierra 130 gr over 56 gr of H4831 and a Federal LRP shoots to 3/4 of an inch. Actually 55 grains shoots even better but I was getting some blow by so I went with the 56 gr. I have found that the 270 is partial to H4831 so that would be a good powder to start with. Good luck and it looks like a great buy and an excellent rifle.
I'm really happy with it...it shoots nice groups, and the .270 ammo is a lot easier to find than my only other "high power" my 8mm Mauser. I just picked up a bi-pod for it yesterday, so I'll try and make it back to the range to give it a go with that later this week.