All barrels show likes and dislikes. As you know, usually the slower the twist, the more powder they'll burn, but if you're not too picky about ultimate accuracy, the slower twists will usually have a wider range of loads they'll shoot with mediocre accuracy. I've a 42" GM .45 with 1 in 60" twist as well. I'd start at 60gr. 3f and go up in 5gr. increments until you get the best accuracy. I use a .445" ball and a 10 pound Denim patch which runs .0215" under the micrometer's anvils. I use Le highvalley lube, or spit. My most accurate loads are 70gr. 3F and 80gr. of 2F. both give the same accuracy and point of impact, and both shoot with identical cleanliness - IE: no-wiping every needed during a day's shooting - whatever the number of rounds. The fouling does not build up but remains easy to push down each time you load. Accuracy is better if shot 'dirty' than if cleaned each shot.
