Pyrodex P does work good in some rifles. The White Rifle System for instance, Pyrodex P seems to be uniform in ignition and because of the smaller granules, might actually assist in getting the large chunk of conical bullet moving. I have shot a lot of P in my traditional rifles. Especially works good for roundballs and in an inline rifle for sabots as well. Its a good powder. ALTHOUGH some rifles just will NOT shoot well with P for some reason. Why, I have no idea. I have three such rifles. If I load RS they are fine. If I load P they are all over the place.

The difference is the screening process in RS and Select. Nothing more. And I have never seen a benefit in accuracy between the two. Although for years, all I ever shot was Select. Until the store ran out one time and I was forced to shoot RS. Well since then I have never purchased Select.