My M&P40c 4" throws my brass into orbit, so I'd like to slow the slide velocity down a bit with a new spring (preferably heavier). I checked Wolff gunsprings but they only have springs for the 4.25" barrel pistols. S&W makes it hard to find parts on their site - where do folks get replacement springs?
Appreciate some ideas.

You could call S&W Customer Service by phone. The parts department will likely have the spring assembly you need.

1-800-331-0852

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Ret. LE, FA Instr, S&W Armorer

1. Smith & Wesson: 800-331-0852

2. Midwest Gun Works: 636-475-7300

3. Galloway Precision: no calls, you will have to use online form:
Contact us > Galloway Precision

I've always received excellent service from S&W Customer Service Phone Line.

For what its worth a flat wire spring for a glock 4" and 4.5" 9mm and 40sw will also work but Galloway states a 17lb spring is stock in both the 9nn and 40sw . My recoil spring is Blue in my 9mm 4" compact. Galloway has 15, thru 20lbs springs depending on your needs, made by IMSA .

I tried the IMSA glock 18lb spring thats in my wifes 4.25 core and it cycles 124gr 1100fps loads just fine with very little muzzle rise but brass lands 3 to 4 feet out . Nice for picking up range brass . Buy some different spring weights and if you use a shot timer you may see what spring works best with split times with a given bullet weight and velocity.

Flat Wound Recoil Spring for Smith and Wesson M&P 9 and 40 M2.0 Compact 4" Pistols > Galloway Precision

This guy should know what springs will work too.

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