To get a slower twist in 45 you would probably have to special order the barrel or even have one custom made. barrel makers can make just about anything you want. Sam Fadala talks about twist rates in his books and speaks of one that is 1-144. It is a 14 ga. but the question was asked in general terms and not specific to any one caliber. I have also heard from other shooters with very slow twist guns of 1-96 or more but don't recall the caliber. Going slower for a 45 may not be practical. The slower twist guns generally use a heavier RB which would work better for your really long distances to retain energy and wind would effect it less.