Oh, and for those wondering why the standard 1911 recoil spring is a "10 pound spring" when neither the pre load nor final load is 10 pounds.
10 pounds is the maximum load the spring should see if you do not want to over stress the wire.
Yes, the spring is over stressed. Most recoil and magazine springs are loaded beyond the "maximum load". This is why they wear out in several thousand cycles, if the loads were under the maximum they would last millions of cycles.
So why are they designed to be overloaded? Space limitations, play around with springs that have a design load of 15 pounds, and have a working length of two inches.