I'm looking to change my recoil spring on my M&P 40. I'm been reading that 11 or 13lb spring people had problems and some say they never had a problem....Anyone change the Recoil spring and whats a good lb spring

Any reason not to use the stock spring? Original was 16#.

Not sure why you would want to change the recoil spring. My M&P 40 has been flawless with the OEM spring and is the softest recoiling .40 that I have shot.

It if ain't broke, don't fix it.

Springs wear out. S&W recommends replacement of the recoil spring at about 5,000 rounds.

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Where do you find where they recommend that schedule?

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I'm making my M&P 40 competition and I heard lower recoil is better but I heard good and bad things....I just wanted to know anyone had any experience if so what's a good Ib spring or its a waste of time...

Change your ammo not your spring for lower recoil. If you want some good advice for competition with a M&P jump over to the Brian Enos forum. Those guys shoot tons of M&Ps for comp and have all the answers.

That light a spring in a .40 M&P would only be good for reduced (minor) power handloads. Some people load to minor power .40 for USPSA Production and IDPA/SSP.
The standard spring is what you should use for most commercial ammunition, and for major power handloads. If you normally shoot heavy loads, you could go up a couple of pounds. To tell if you hae the right spring, your empties should be landing 3 to 6 feet away. Too light a spring batters the gun (and may cause misfeeds), and too heavy for the load causes functional problems.

The ISMI springs on the stock S&W assembly are as good as you can get, and far superior to piano wire springs. You can get the ISMI springs/assemblies from Brownells.

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