M&P 40 to 9mm barrel swap

[CNobbe]

It seems like Storm Lake has discontinued their M&P conversion barrel for the M&P 40, but I recall reading that the M&P 9mm barrel will drop in the .40 slide. Can anyone verify?

I run a Glock 22 for bowling pin league, use a Lone Wolf 9mm barrel occasionally. I'd like to add M&P 2.0 to the collection, debating getting the 9mm or the 40 and conversion to 9mm if possible.

 

[kcofohio]

From time to time, S&W factory barrels show up on eBay. That is where I got a factory M&P 357 SIG barrel at. Also, Barsto barrels. A bit more $.
https://barsto.com/product-category/barrels/smith-wesson-mp/

I think Apex Tactical also carries conversion barrels.

 

[9mmepiphany]

I'm not sure about the 2.0, but on the original models the factory 9mm barrel diameter is smaller than the .40...which places the striker out of alignment

 

[Mike J]

A member here posted that he had gotten a S&W 9mm barrel from Midway USA. He stated he had been using it in his M&P 2.0 Compact. I am sorry but I can't remember who it is right now. Midway notified me the other day they are back in stock but I don't know if they still have them or not. I decided that in the current situation I am not buying one. I was wanting to use it for cheaper practice.

 

[Unemployedshooter]

Bought a SilencerCo brand conversion barrel in 9mm for my .40. Dropped in and shot fine (good lockup). Not sure they still make them, though.

 

[Steve in NC]

I'm not sure about the 2.0, but on the original models the factory 9mm barrel diameter is smaller than the .40...which places the striker out of alignment

This is incorrect. It's not the diameter that is different, it is the width of the barrel hood that goes back into the top of the slide at 12 o'clock. And this is the same for Gen1 and M2.0 models. The width of the barrel hood on a 40S&W barrels measures .42X". A 9mm barrel will measure .39X". All barrel diameters at the lockup points are the same between the calibers and generations of manufacture.
So yes you can drop a factory 9mm barrel into a 40 cal M&P firearm and mechanically it will work. But I've see strong arguments from some on other message boards saying do not do this or under certain scenarios it can be catastrophic. So to be on the safe side use a true 40/9 "conversion" barrel and not simply drop in a factory 9mm into a 40 S&W slide/frame. I personally haven't seen conclusive evidence saying one side or the other of this debate is correct. I run an old Storm Lake conversion 9mm barrel in my original 2009 era M&P40c. Have thousands of 9mm rounds through it with no issues. But this is a true 40/9 conversion barrel. The hood measures .426". So you can not take a true conversion barrel and put it into a 100% factory 9mm slide/frame. It will not lockup.

Not trying to argumentative at all. Just wanted to make sure all info is out there is accurate and available for any readers to evaluate this themselves before modifying the factory setup.

Be safe and stay healthy,
Steve

 

[wally]

I'm not sure about the 2.0, but on the original models the factory 9mm barrel diameter is smaller than the .40...which places the striker out of alignment

Not true,The 9mm barrel hood is smaller than the notch in the slide and the ejector and extractor are ~0.5mm away but surprisingly it doesn't matter. I've a S&W M&P Compact in .40S&W and dropped in a S&W M&P 9mm compact barrel that I got as a replacement part from Brownell's. I did need to buy 9mm M&P Compact mags or use 17 round 9mm M&P mags with a spacer on the bottom. You don't need the spacer for casual range use, its there to prevent over insertion. I had read that the .40S&W mags "worked" my experience was "sort of" the rounds weren't retained reliably -- I'd get some stovepipes or sometimes find loaded round ejected with the empty case. Again for casual range use this might be acceptable.

I've shot probably 100X more 9mm rounds through the gun that .40S&W rounds. For my carry compacts and sub-compacts I generally carry the .40 and get the 9mm for practice, price difference in practice ammo pays the the second gun in a reasonable amount of time (typically 50-100 rounds a week). For the M&P .40 Compact all it cost me was $65 for the replacement 9mm barrel and the price of a few 9mm mags.

I don't know if this is the still true for the 2.0 versions.

 

[commygun]

My MP40C runs flawlessly with a factory 9C barrel I got off of eBay.

 

[scaatylobo]

It seems like Storm Lake has discontinued their M&P conversion barrel for the M&P 40, but I recall reading that the M&P 9mm barrel will drop in the .40 slide. Can anyone verify?

I run a Glock 22 for bowling pin league, use a Lone Wolf 9mm barrel occasionally. I'd like to add M&P 2.0 to the collection, debating getting the 9mm or the 40 and conversion to 9mm if possible.

FYI = when I got my new in the box S&W M&P .40,I called Smith and they told me that a barrel swap was not available for that model.

Sad,that I went back to my Glock as an EDC and all the calibers that I could use in the G-19 frame.

 

[RUT]

I have an S&W 9mm "conversion" barrel for my M&P 40 full size and it works just as well as the .40 barrel. I change the barrel and magazine, and that's all there is to it.

 

[d'zaster]

I have a shield 40 and recently got a LWD alpha wolf 9mm conversion bbl & Shield 9mm magazine. It works and lock up is good. I considered running a stock 9mm bbl but after reading conflicting info, I went with aftermarket conversion route.

 

[kcofohio]

I have a shield 40 and recently got a LWD alpha wolf 9mm conversion bbl & Shield 9mm magazine. It works and lock up is good. I considered running a stock 9mm bbl but after reading conflicting info, I went with aftermarket conversion route.

I bought that same barrel. It has been flawless.
I also bought this barrel.
https://www.tr-enabling.com/product-p/ba-p-mps-40-357c.htm
But I don't run full throttle reloads through it.

 

[GooseGestapo]

I’ve got both a .40 Shield and 9mm. The 9mm barrel will work as well as feeding 9mm from .40mags and vice versa. I haven’t tried the .40 barrel in the 9mm slide however. Only difference I’ve noted with mags are the witness holes for round count.

I got the 9mm to practice with, but carry the .40...
I put talon grips on the .40 frame for better control.

If anything, the .40 is more accurate. Not to mention more powerful...

I recently got BearCreek Arsenal barrels for my M22 Glock. The 9mm was satisfying accurate, but the .40 replacement barrel is astonishing. 5” to <2” accuracy at 25yds. 100% reliable. $43 delivered!!!
G22 is a late ‘95-early’96 Gen 2. Has my badge # serial #.