critter68
You didn't mention distance you intend to shoot but for 100-200 yards a good place to start for breech seating a 38-55 is 18.0-18.5 grains IMR 4227. A large rifle primer will probably give best results but don't rule out large pistol primers. Seat bullet so its base band is engraved by the rifling for about half its width. That is usually about 1/16 inch ahead of the case mouth.
For shooting a bullet that heavy from the bench, your Pedersoli might beat you up some. A bullet of 300-330 might be more enjoyable from the bench if you shoot a lot. Offhand, the 360 gr bullet shouldn't recoil too badly.