Are the taper pins for the FSB’s have a standard distance apart??? Just kind of curious to know.
No, they are not. The holes for the FSB are drilled after it is installed on the barrel. Once drilled they are “proprietary/mated” for/to that particular barrel. Conceivably, some, from the same manufacturer and production run, may be interchangeable but you cannot count on it and I have never seen it. I have installed “used” FSBs on new barrels but it is more of a pain that way.
I never could figure out why just about everything else on the AR is precisely located, but this is more or less just “eyeballed.”
Because it would needlessly raise the price to make them precise/interchangeable. Just a guess.