The spring is in the handle. Remove the grips, use a punch to push out a pin, pull out the punch, the lanyard loop hole pops out *under pressure* to reveal the spring. The spring is over a metal rod. Take out the spring, slide the new D spring over the rod, put the lanyard loop back in, line up the holes, push the lanyard loop down against a table or something sturdy until it compresses the D spring enough for you to push the pin back in. Put the grips back on. Done.
Here is what I used to help me do mine. Wonderful diagrams:
http://www.geocities.com/Yosemite/6078/mainten.htm
I know nothing about guns, probably use the wrong terminology, but it was easy to do. This was on a 92FS.
When you order the spring make sure to get one that is #18. There are other varieties of springs for sale that go lower. Stock spring is #20.
I read this somewhere in this forum, it's a direct cut n paste from a word document:
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Statistics of three springs:
92FS--Trigger pull factory spring = DA 11.8lb
SA = 5.55lb
Trigger pull with "D" spring DA = 8.10lb
SA = 4.00lb
Trigger pull with "Comp" spring DA =8.0
SA = 3.8
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I've heard people say not to use the competition springs for defense guns.