66" twist will shoot 245 & 295 well.... if you increase the powder charge as the Powerbelt grain size increases.
48" twist shoots 245, 295 & 348 well. Again... increase charge as lead increases.
28" twist shoots all the Powerbelts pretty well. But with this twist, I found decreasing the powder charge as the lead increases helps accuracy. Hypothetically, you may use 105 gr with 245 ... then only 75 gr with the 405s.
No science major in muzzleloading ... just my opinion here.