Elkins45
Member
I have a full size M&P 357 Sig that I want to convert to 40 S&W to take advantage of cheaper ammo. Can I just drop in a 40 barrel or do I need to change the recoil spring weight as well?
Recoil spring strength 40 vs 357 Sig?
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Those 16lb springs were from the early years of the 1.0 series I was told they were changed to a 17lber some later after dumpng the 357sig from the line up !? I was told by s&w CS the 2.0 40sw runs a 18lb springs . I also found this spring runs well in my wifes old 4.25" full size core 9mm for many years . I run a 20lb spring in my old 4.25" full size m&p 40sw and that runs fine with standard 40sw loads and with 155gr underwood HP ammo . I also have a 5" 40sw thats running fine with a federal factory or my reload ammo with the 18lb factory green spring .
By the way a glock 17 gen 1 thru 3 springs are the same length and work fine in the m&p .
By the way a glock 17 gen 1 thru 3 springs are the same length and work fine in the m&p .
I've had two different companies - Sig Sauer and Rock Island - tell me that their 357/40 pistols use the same recoil spring.
I got sucked into the modular caliber thing with Sig Sauer years ago... they use the same spring for 40S&W and 357SIG..
I went the other way. I converted my 1.0 M&P 40c to .357 SIG. I did not change the recoil spring. I have since shot nearly 3,000 rounds of .357 SIG with no problems, so I expect that your .40 will do just fine with the original .357 spring.
STORMINORMAN
Member
Works great in the both fullsize & Compact M&Ps (& with 9mm as well) in my experience...
Also in the FN FTX, for what that's worth.
Cheers!
Also in the FN FTX, for what that's worth.
Cheers!
I went the same way. I have an M&P 40, a 40 Compact and a Sig P229 that I have done the barrel swap on plus a G32. You can't beat the accuracy of the 357 Sig and it is a pretty stout round as well. I cast my own bullets and PC them. I don't push them quite as hard as the jacketed bullets but it is still an attention getter at the range when people think you pulled out a 9 or a 40.
Clete Torres
US Veteran
You wouldn't consider selling that would you? I have the compact version and I've been kicking myself for years for not getting the FS at the same time when I had the chance.
yes, I have both a P226 and 2 P229 40 and 357 sig use the same spring.
FWIW, my P229 uses the same spring for the 40 and 357 and works flawlessly with both cartridges. Have no idea how many pounds it is.
Most seasoned shooter would not feel the difference in a spring thats slightly heavier or lighter but if your good at placing a number of rounds of several targets quickly you will see the difference with a shot timer and it all depends on the load you shooting . Buy a few different spring and try them and make up your own mind .
One of my two carry guns is an m&p 4.25" 40sw filled with 155gr underwood load that averages 1318fps with a 20lb recoil spring . But its tested and reliable with both hst 180gr and ranger t series 180gr standard pressure ammo but I can see it go nose down when chambering the next round so 18lb spring would be better for that load . My typical practice load is a 155gr at 1280 fps and the 20lb springs feels about right and it shows with a shot timer too .
Figure out what works best for you and the load you shooting . If you see your pistol when going back in to batter and go nose down your recoil spring should be lighter . When my wife was shooting local uspsa with 147gr 890fps minor PL load in her m&p core the recoil spring will be a 13lb spring but when I used it at major PL an 18lb spring worked well .
Figure out what works best for you !!
One of my two carry guns is an m&p 4.25" 40sw filled with 155gr underwood load that averages 1318fps with a 20lb recoil spring . But its tested and reliable with both hst 180gr and ranger t series 180gr standard pressure ammo but I can see it go nose down when chambering the next round so 18lb spring would be better for that load . My typical practice load is a 155gr at 1280 fps and the 20lb springs feels about right and it shows with a shot timer too .
Figure out what works best for you and the load you shooting . If you see your pistol when going back in to batter and go nose down your recoil spring should be lighter . When my wife was shooting local uspsa with 147gr 890fps minor PL load in her m&p core the recoil spring will be a 13lb spring but when I used it at major PL an 18lb spring worked well .
Figure out what works best for you !!
oworthsr
US Veteran
The .40 cal recoil springs in my two M&P Compact 2.0's (3.5" and 4.0") function equally well whether I shoot .40cal rounds or .357 SIG rounds. Drop in the barrel I want, load up the (same) mag with proper rounds, pull the trigger. Goes bang every time with no FTF issues at all.
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