Do NOT get a 1/48 twist! This is a compromise between conical and round which shoots 6 " groups of anything in all three of my rifles (all 1/48 -TC .50 Hawkin, TC 45 Seneca, Cabelas .45). Decide between conicals or round, and get the proper twist rate for it. And 1/48 IMO isn't!!!
Wow, you sure have bad luck with your guns! I've had several 1:48 rifles (including a .45 Seneca) and none shot that bad with PRB or Maxi Balls. Not sayin' it's an ideal twist for either, but with the right powder charge it does okay with both.
