I cannot tell you for certain but I dropped a 13# IMSI glock 17 spring in my M&P40 and it feels the same. Not scientific by any means but it is close enough for me.
Dan Burwell said:Here is my questions and the responses(bold) I got from a S&W engineer:
2. What are the recoil spring rates you guys are using in the 9, 40, 357 (currently we use the same spring for all three 9/40 and 357, in the future we will be using a heavier spring in the 40 and 357 as far as spring rates they are something like this;
current 9/40 spring "marked blue"
future spring for 40/357 and possibly 45 spring "marked green"