[Lurch37]

Midwest sells a Wilson reduced power 18lb, a Wilson reduced power 19lb, a Wilson USGI style 23lb, and Wilson extra power 25lb.

For Colts, Wolff's website lists 15lb thru 21lb as reduced power, 23lb standard, and 25lb thru 34lb as extra power. It also lists a 21lb mainspring as factory from Kimber.

I am also of the opinion that the standard weight of the hammer spring in a 5" Govt 1911 is 23lb with a 16lb recoil spring.

Kimber's website sells a 3 spring kit with only the recoil spring weight given, (16lb).

I read a 2012 thread on 1911.org that says that Kimber puts in 21lb hammer springs.

As the above shows, there are many options to your question.

Although the Kimber rep said 18lb, that seems light to me. I have yet to find any specs on a Kimber mainspring weight from Kimber themselves.