I've been competing long enough that I have had 2 .45 comps built (not drop in). The second was a very big mistake on my part!!! More $$$$$'s than sence. To make a .45 comp work you would have to shoot something like a 152 gr. cast swc at major power factor of 165. This is safe and makes the comp work but it is only good for competition and plinking and you are at a serious disadvantage in competition because most if not all race guns will hold 27 + rounds in a "Big Stick" whereas .45 will only hold 19/20 maybe.
FWIW
Richard