Rigby, I am not really sure what question you're asking, but I shoot the Snover in my Browning 40/65 and can tell you what I do.
My bullet casts at .410" and I shoot it unsized. It touches the beginning of the rifling at an overall length of 2.88", so I seat it to 2.87" OAL. I use reformed Win 45/70 cases, and 60 grains of Goex Fg will be compressed about 0.24" (use a compression die), and it gives me a MV of about 1150 fps. Accuracy averages 1.5 MOA.
I prefer to shoot unsized bullets, but if you are going to size your bullet, I would size the entire bullet to .4095" and see what OAL is when you do that. It might be a bit longer that what you're getting now. I don't like blackpowder bullets to actually touch the rifling, even if that may give me better accuracy, because after a few shots, as the black powder fouling builds up a bit, it becomes hard to chamber a round. I use a blow tube. If you wipe between shots, then, of course, this won't be a problem.
BTW, that Snover design in 40 caliber is an outstanding bullet. I think it is the best long range 40 caliber design available in a non-custom mould, and if your Lyman mould produces a good bullet that shoots well, I wouldn't look any further for another bullet.
