I tried one can of Pyrodex in the late 70's, this was just before the plant blew up. Once was enough, only real Black Powder for me. I don't see any good reason to have some Pyrodex on hand.
I've been in this game since 1976 with both caplocks and flintlocks, on the shooting line and in a tree stand, plus regular shooting on my private range. This translates into a lot experience. Most of the guys on this forum also have a lot of experience, some more than me. I would listen first and last to what these guys say about Pyrodex.
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I have on hand a quantity of 2fg, 3fg, and 4fg. But I now only shoot 3fg up to .54 caliber. And I agree that 2fg or 3fg works well as a prime but I still use 4fg for all my shooting. I live in an area that's hot and humid and years ago I did have problems with 4fg as a prime, but I just worked out my problems and now it's all I use.