First step, as with anything new, is to do a chamber cast to determine throat diameter and select whatever cast bullet matches that, or really close. If that detail is attended to then for 1400fps, give or take, I would employ an alloy in the 9-11bhn range, gas check optional if 1400fps adhered to. A good lube on a naked lead bullet will suffice, especially at low velocity. I'm slowly recognizing the worth of powder coating, but view it as an expedient for using really soft alloys (for reliable expansion) at higher rifle velocities. (Even at that, traditional naked bullet approaches work A-ok if strict protocols are adhered to, so the jury hasn't fully decided yet!)
The only times I got my t*t in a wringer with poor performance was when I brazenly went at it without first doing a chamber cast. Sometimes you get lucky, sometimes you don't, because every gun maker who ever drew a breath has had their own ideas about chamber/throat/leade dimensions (SAAMI standards notwithstanding, they only go so far), and there are always tolerances in machine work plus tool wear - so a wise guy shouldn't assume anything.
