I use 4F for prime when plinking at the range because I bought two cans of it several years back. Enough for a lifetime supply, since that is all its good for. When hunting I use 2F in the horn and prime with it also. Usually fill the pan almost full because it takes up more space and when priming from the horn, it's hard not to anyway. I have tried both with back to back shots at the range, and if there is any difference, I can't differentiate one from the other. Trying to fiddle around with two different powders while in the woods is for the birds.