I recently purchased a new full size 2.0 M&P .40 cal, and wanted to report that I ordered and received a new Storm Lake .357 Sig barrel for it. I am pleased to share that the barrel, dropped right in with no binding, stiffness or difficultly. I didn't have time to go to the range, but I fired 4 full magazines in the back yard and the pistol functioned 100% and accuracy was perfect.
I now have a 2 calibers for 1 pistol......

You could also get a 9mm conversion barrel and have three calibers in one pistol. With the appropriate magazine, of course.

.40 to .357 sig is usually the easiest conversion since the sig is essentially just a .40 case necked down to 9mm. magazines and breech face are the same so you don't the potential issues with feeding that can happen in the .40 to 9mm conversions because of the sideways slop in the breech face. I've never run into any issues with my .40 to 9 glock conversions but I understand that it happens from time to time. Still i will be getting one of the apex .40 to 9 conversions for my PC CORE .40 upper very soon.

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Equal opportunity shooter

I had an opportunity to make a range trip, and I am extremely pleased with the Storm Lake barrel, it's true drop in, it's reliability in the pistol and the accuracy achieved with it. I fired 400 rounds of Georgia Arms bulk pack, 125 grain FMJ @ 1,300 fps. No malfunctions and POI was right on.
I am skeptical and doubting by nature, but the Storm Lake barrel exceeded my expectations.

Get ya a couple boxes of Sellier and Bellot 357 sig, good ammo , close to full power and can be had at a decent price.

Good to know Ohiofrank!
I did buy some Underwood Item #149, 125 grain Bonded JHP @ 1475 fps.

Did you detect much increase in recoil with the .357 Sig rounds vs the .40? My pistol arrives Tuesday and I'm thinking of doing the same thing.

It's normally the opposite -- the 357sig recoil is easier on the wrist than the 40S&W. I have over 15K rounds of full load 357sig on my 2 M&P's and prefer it to the 40.

It's even quite workable in the Shield with the RemSport 40-to-357 conversion barrel.

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Clyde Washburn
NRA Cert Inst

Interesting. That does seem to check out now that I crack open my Cartridge Comparison Guide. Hard to compare because of the different grain weights but one Winchester example I see of 180gr .40 is a few percentage points higher in recoil than 125gr in .357 sig.

I also purchased the Storm Lake .357 Sig barrel (part no. 34116) and can also report it dropped right in and seated perfectly on my 4.25" full size 2.0 M&P 40. I've only fired 1 magazine so far but it worked without issue.

Unlike what others have mentioned, the recoil was definitely more intense on the 357, compared to the 40. Of course that is round dependent but I typically buy the cheapest FMJ brass I can find on sale. In this case it was 180gr Winchester for the 40 (1020 f/s, 416 ft-lbs) and 125gr Lawman for the 357 Sig (1325 f/s, 487 ft-lbs). My hand was hurting by the time I shot that 15th 357 Sig round.

Anyway I found that barrel on ebay for $129 (despite their warning that it didn't fit version 2.0 guns):
Storm Lake S&W M&P 357 Sig 4.25" Stainless Steel Barrel 34116 | eBay

Heard that the 357 SIG is earsplitting. Anybody shot one with little to no hearing protection? Like when it'd be used in a self defense situation.

It definitely sounded louder (compared to the 40) to me through my 34dB muffs. Maybe similar to a 357 magnum, although I didn't have my R8 with me that day to compare.

I did this to my 1.0...awesome!!!