Most makers these days go with a 1 in 48" twist with good accuracy in a .40, though the old Douglas barrels were 1 in 66" and were also very accurate. My last few .40s have been 1 in 48" with excellent accuracy, and I wouldn't hesitate to own another such barrel. I think that 1 in 48" barrels got a reputation as a compromise twist rate from TC when they picked that twist as the most likely slowest pitch with which to shoot conicals, and the fastest to shoot round balls. They then rifled their barrels shallowly for conicals which probably hurt their roundball accuracy unless very tightly patched and kept very clean between shots. At least that is how I remember mine. I have an old Douglas .54 1 turn in 48" barrel that will open your eyes for accuracy because of the deeper rifling. So if I were buying a barrel today, I would probably go with whatever twist the maker uses, and be confident in the fact that it is hard to buy a bad barrel from a "name" maker.
Roger B.
