Is it just a simple drop in/barrel switch conversion to convert a full size M&P .40 to .357SIG?

Also, does anyone know if Smith sells .357SIG barrels for this purpose?


I have read about the Storm Lake converter but it seems sketchy at best.

Any/all feedback appreciated. Thanks

There is a .40 FS with a .357 sig barrel in the Classifieds. Looks like Barrel and Mags is all you need. I could be wrong though.
You mite send him a pm. He has it priced With and Without .357 barrel.

Guy goes by. Toocool.

Hayden.

The magazines are the same.
A factory barrel will drop in and work just fine.

I haven't heard S&W blessing the use of factory barrels for shooting different calibers. Could be a liability issue, could be a customer service issue. I just know a lot of guys on this forum have done it and fired hundreds of rounds without a hitch.

It's just a matter of swapping barrels. From the factory they use the same magazine. Midway has barrels for $78 Barrel S&W M&P 357 Sig 4-1/4 By the way, I wouldn't hold off too long as once they sell out it can be 3 or 4 months before they're in again. When the 9mm barels came in they sold out in a couple of days.

Thanks for the info. I've been trying to read up on Storm Lake match grade barrels but I haven't been able to find much other than a few listings on Brownell's.

Has anyone heard anything regarding the quality/durability of the Storm Lake barrels?

I've just seen guys post here that they send their SL barrels back because they won't work. They need gun smithing to fit.

You should do a search because a lot will come up.

FYI S&W sells/sold a kit with both the 40 cal and 357sig barrels along with 3 mags. This is what I picker-up in 2010 it was an LE combo. The slide is marker 357 sig. but the 40 cal. barrel is in it the most! I also got the S&W 9mm and the proper 9mm mags never any FTE's etc. probably well over a thousand rounds through the combo's without a glitch. I am also probably over 600 rounds with the guiderod version of the lasermax and not one problem using all three barrels...

I have both a compact as well as the 4.25" fullsize 40 caliber M&P in my compact I have a Storm Lake 357SIG barrel and in the 40 fullsize I have the factory Smith & Wesson 357SIG barrel and I will state this in both weapons I shoot better with the 357SIG ammunition but it is not cheap so I do not practice with it as much although with my full size I am thinking of leaving the 357 barrel and loading it with the hollow points that I have for around the house, as I carry my 40C daily to work and back home!

__________________
59,M&P9,40,40C,357,(2)45,G26

Yes you can although they seem not to want to sell them to you wink wink if you know what I mean but you can get the 40cal fullsize 9mm and 357 sig barrels have all 3 cal's in 1 gun which the 357 sig rnd is nothing more then a 40cal round with a 9mm bullet in it when you convert the 40cal down to 9mm you have to use 9mm mags you can use 40 cal mags with the 357 sig

Your switch to 357 from 40 is as easy as dropping in a new barrel. As stated earlier you can get factory barrels from Brownells. I've used Storm Lake 357 barrels in 3 conversions, so far: 1 Glock 35, 1 Springfield XDm, and 1 Kimber Eclipse. These barrels have been great, with an increase in accuracy each time. The Kimber had to be fitted, which was no surprise, due to the tight tolerances of the brand. The SL conversions function 100% and have many rounds through them so far with no problems. I had to go to KKM for a barrel in my M&P 40L, because SL doesn't make a conversion barrel for the long slide models, and apparently have no plans on doing any.

__________________
Tom
"Panem et Circenses"

Mind if I ask why you'd want to make the conversion to 357 sig over 40 S&w ?

Just an FYI... some of the best prices on .357 Sig ammo can be found at Underwood ammunition and SGammo.com

Oh... now I hate you all. I had my mind all set on my next gun... I was getting a little snub nose revolver that I could conceal carry. BUT NOW that I joined S&W Forum today, and I learned that the .40 can be a .357 sig with just a barrel swap... well now what am I supposed to do!?I already have a 6906 (larger frame) and a little Kahr CW40 (for daily CCW). So I can't use the "well I don't have that size gun" as logic. That leaves me trying to make a choice between another home defense/range gun or another daily CCW (revolver). What to do, what to do???

This is the way I received my LNIB M&PC .357 Sig.

It also had Trijicon Night Sights, and was never fired. (except at the factory)

I was told that it was originally a LE gun, that was never issued.

I have found the sights to be off by about 2 in at 25 yards when using either a 357 barrel in a 40 slide or a 40 barrel in a 357 slide. Other than that all is well.

jdh- You mentioned rounds were 2 inches off. I noticed that when I put the .357 barrel in a .40 gun, the round were about two inches low. In its factory condition, rounds were on target. Is this consistant with your results? Do you think that a 'conversion' barrel would eliminate the difference? also considering an adjustable rear sight? Any thoughts?

About the easiest thing you can do to correct your 2" low problem is to aim 2" high, starlifter.

__________________
Former USN, Retired US Army

When I first began exploring CCW I thought I could never conceal a full size pistol and bought a .380 Bodyguard. I have since purchased a full size M&P and have discovered how easy it is to conceal it. I purchased a 40 and will eventually purchase the 357 barrel.

Looking at posts and reviews on a lot of sites, it is clear that lots of people use a S&W 357 SIG barrel in an M&P 40, and get excellent results. Any time you fit a major component like a barrel, you should not be surprised if you need to do some fitting, but the S&W factory replacement barrels seem to be properly toleranced to work nearly every time without fitting.

Storm Lake barrels are "match grade." Any match grade component is going to be tighter-fitting than factory replacement parts. This is to allow hand fitting for a precise fit. Since modern manufacturing methods allow much closer tolerances than just a few decades ago, match grade components will more often function without modifications, but you can't count on it.

When a properly fitted match grade barrel is installed, you can expect a noticeable improvement in accuracy, but should also be aware that you can get less functional tolerance to dirt, temperature and other adverse conditions.

As for magazines, both magazines that came with my S&W 40c have both "40 S&W" and ".357" stamped on them, even though S&W does not presently make a 357 SIG pistol that this magazine would fit.

The simple answer is, performance. .357 SIG in a 4" barrel has no trouble consistently exceeding 1400 fps with 125 gr bullets, with many (not all) brands of ammo. Velocity is more consistent, accuracy quite good. More velocity = better penetration, more reliable expansion, better long range performance. People switching from 40 S&W to 357 SIG often report better accuracy with 357 SIG.

I have been reloading for years, and I have noticed that a light bullet, high-velocity load will shoot lower at short ranges than a heavy bullet loaded to lower velocity, fired from the same gun. I would absolutely expect a 125 gr bullet at 1400 fps to hit lower than a 180 gr bullet at 1000 fps at 25 yards (100 yards in a different story), no matter what gun I fired it from. I expect this is because the fast, light bullet zips out of the barrel before the pistol recoils enough to change the point of impact as much. A heavy, slow bullet makes the pistol whip up just a little more before it gets out of the barrel, shifting the point of impact higher.

My Storm Lake barrel dropped right in my 40 CORE. It now lives in my 9 Pro. Dropped right in there also. BTW CS at SL is great. KKK barrels is also good and check out Carver Customs.

__________________
USN Retired/VN VET
M&P X5