I notice there is quite a variety of replacement
recoil springs available for the 1911 .45ACP. How is the strength of the spring measured, that is, to what length is the spring compressed while measuring it? Or is it generally identified by wire diameter, length and number of turns?

Bud W

The measurement is taken at the compressed length.

Depending on you technical you want to be, you can mark both the end-points of the spring on your frame and slide, then move the slide rearwards and measure.

I don't know what that length is, and I'm too lazy to go and measure any of my guns right now, but a google brought up this page, which suggests it is 1.6"

http://www.realguns.com/Commentary/comar16.htm

Thanks Mark... appears to be just what I was looking for!

Bud W