the 45 acp has 100 years of combat experience under its belt...it is a proven round...the 40 cal was a stop gap measure thought up by the brilliant minds at the fbi...they adopted the 10mm as their duty side arm and the female and smaller handed male agents couldnt control the recoil, so the fbi armorers cut the round down and thus the 40 was born...it is perhaps the most perfect example of mediocracy that ever existed...