I would second the recommendation for the Wilson 18.5 in a 1911, 45 ACP. For me that seems to get the best results in my Wilson CQB and S&W Pro 1911. That spring tames heavy hitting defense loads, and also works flawlessly with SWC target loads. In a 9mm 1911 I use either a 12 or 14 pound spring. The 12 is fine for standard pressure loads up to 124 grains, but for +P or +P+ (or standard 147 grain bullets) I step up to a 14. The gun will run with other spring weights, but these seem to "feel" right.