It probably could be, but like you said... The rifling would absolutly HAVE to line up. If it wasn't line up, then when the pellet transitions from one piece to another it'll end up being engraved a second time probably causing leakage due to the second engravings being out of phase with the first. Acuracy may suffer, velocity definitly will.
There would also be the problem of Bore Alignment. Unless they're mandrel rifled, the bores of most barrels aren't completely straight. There may be .001" or 2 of run-out. So even though the OD is nice, lined up and square the ID may be offset a hair causing shaving. Now, if you got the bores lined up perfectly, there may be an outter barrel offset. Probably not much of one, but enough that it would end up annoying someone like me.
