I read an interesting comment from doc white on the 1:28 versus 1:20 twist. Here it is:

Seems to me that it would be intuitive to know that there is no such thing as a single twist that is effective over all the ranges of bullets lengths, weights and velocities. Truth is that each bullet (of whatever length, weight and BC) has its own particular twist requirements at each velocity that it is shot at. Long term studies over the past 100 years have shown that optimum twist for really long bullets*like 460-520 gr in 450 caliber require twists of 1-18 to 1-20. I just ordered a 458 barrel*for a 45-1 7/8" cartridge (the*45-110) with a 1-18 twist. I intend to shoot 520 grain bullets with about 75-90 grains Black Powder at more or less 1200 FPS for long range cartridge. This is exactly the load I use in my muzzleloading Whitworth copy with the same bullet but a 1-20 twist, and I win 700 yard matches with it. If you want to shoot*puny pistol bullets in a 45, using sabots, like many of our modern hunters are doing, then 1-28 might be OK, 1-32 might be better, depends on the BC and the velocity of the*bullet. The BC of a .450 caliber 520 grain bullet is .36, BC of a .357caliber 158 grain saboted pistol bullet is .18 or worse, some as low as .12. Obviously, a single twist won't cut it with both bullets. Also, obviously, the bigger slower bullet with the higher BC will have far higher downrange energy, penetration and knockdown than the puny pistol bullet despite the pistol bullets flatter shorter range trajectory.*