M&P .40 with option to use 9mm barrel?

[mptoledo]

Rather than starting another thread, I thought I would just tag my question on the end of this one

I was told you can't/shouldn't use a "factory" SW 9mm barrel in a 40cal gun. Something about the breech being fractionally smaller.

Is this true or is it safe.

The reason I ask, I have a M&P9 threaded and have a 40 coming(someday) in the mail(ffl). I wanted to keep the factory 9mm threaded barrel and sell off the gun with the "standard" factory barrel(came with both).

 

[Smitty357]

Rather than starting another thread, I thought I would just tag my question on the end of this one

I was told you can't/shouldn't use a "factory" SW 9mm barrel in a 40cal gun. Something about the breech being fractionally smaller.

Is this true or is it safe.

The reason I ask, I have a M&P9 threaded and have a 40 coming(someday) in the mail(ffl). I wanted to keep the factory 9mm threaded barrel and sell off the gun with the "standard" factory barrel(came with both).

If this were true, those of us who have converted our Shield .40 to 9mm for that past few months would have already blew our hands off.

I've been shooting my Shield .40 with the factory 9mm barrel out of my Shield 9mm since September. Recently I purchased another 9mm barrel for the puprose of letting my ole lady carry the Shield 9mm on her at all times. Now i have a 9mm barrel for my .40 to shoot at the range.......No problems since September and i've put well over 3K rounds through it.

 

[2001gmc]

If this were true, those of us who have converted our Shield .40 to 9mm for that past few months would have already blew our hands off.

I've been shooting my Shield .40 with the factory 9mm barrel out of my Shield 9mm since September. Recently I purchased another 9mm barrel for the puprose of letting my ole lady carry the Shield 9mm on her at all times. Now i have a 9mm barrel for my .40 to shoot at the range.......No problems since September and i've put well over 3K rounds through it.

Smitty do you use the 40 mags to shoot the 9mm rounds or did you purchase a 9mm mag also for your shield?

 

[bobnieder]

Man, I don't have anywhere near 3K rounds through my FS .40 with the 9mm factory barrel -- only a little over 600 rounds, but Ii will say that my accuracy has been the same or better with the factory 9mm vs. the .40 cal. barrel. And as far as the 9 mm mags go, no feed problems at all, so I would recommend getting the 9mm mags.

 

[mptoledo]

Thanks for the input. Being unfamiliar with the M&P line, I wanted to make sure I didn't do somehting stupid

I have owned many of the Revolvers, 629,686, 2x 500's and my current carry is a 360pd(357mag).

 

[1sailor]

I'm coming in on theis thread a little late but here goes anyway. I have an M&P40 that I picked up a 9mm barrel for and after about 200 rounds picked up a couple of 9mm mags also. using the 40 cal mags i often would not feed the last 9mm. since picking up the 9mm mags I have put close to 6000 rounds of 9mm down the pipe and do not recall a single malfunction. Accuracy is on a par with the .40 cal from a sitting position at 50ft and a little better shooting offhand at the same range. typical groups sitting are a little under 2" with 10 rounds.

 

[Smitty357]

Smitty do you use the 40 mags to shoot the 9mm rounds or did you purchase a 9mm mag also for your shield?

I currently use the 9mm mag and the 9mm barrel when shooting it in my .40. I do this because I have used the .40 mag with the 9mm barrel, but I often came across some FTFeed) issues. Mostly towards the lower capacity part of the mag.

The 9mm mag just assures you that it will feed the 9mm rds properly. So just get a 9mm barrel and a 9mm mag, u'll be good to go without issues.

 

[TxAggie]

On a similar note, I recently purchased the M&P 9 full sized before hearing that you could put a 9mm barrel into the .40. I did this mainly because the 9 is cheaper to shoot, however recently it has become VERY difficult to get it where I , but .40 is fairly plentiful.

Is it possible to put a .40 barrel into a 9mm? If not, how about a full .40 slide?

Thanks for any input.

 

[mptoledo]

You guys need to please specify when you say a "9mm barrel". Are you talking a "factory" barrel or "aftermarket" barrel?

I have heard the stormlake conversions are made exactly to spec as the 40 "factory" except for the bore size. Meaning it will seat perfectly in the 40cal gun. Where as the 9mm is a bit thinner and doesn't seat "perfectly" in the 40 cal.

Thanks, MP>

 

[bobnieder]

Do not try to go the other way (9mm slide/frame with factory .40) -- it will not fit together.

And Smitty and robkarrob and I are all talking about factory S&W barrels, not aftermarket barrels by another mfr.

 

[mptoledo]

Thanks for the replies. I have the 40 sitting at my FFL and will pick up friday along with 3 ar lowers I took my 9mm with threaded barrel out to the range for the first time and it was nice and accurate. I put my YHM cobra 45 suppressor on it(got the adapter from YHM) and it would not cycle. It would shoot the first round fine, but wouldn't push the slide back far enough to cycle the next round..

Do I need to get a different spring for it to work properly?

By the way.. I used American Eagle 147 gr and it was stupid quiet!! Much quieter than the 22lr 2 benches down from me!!

PS, Yep, aware of the not going to a 40cal on a 9mm, but thanks for looking out for me

 

[sdeeut69]

SW .40 - 9mm Conversion

I too was just looking at buying the M&P 9mm and then started browsing the forum and read about the .40 conversion to 9mm. So I went to the local gun store and rented the .40 to see how it felt... WOW! It was amazingly accurate and softer than my friend's .40 glock we had with us. So I have decided that's the route I'm going to go, buy the M&P .40 and the aftermarket barrel with 9mm mags.. but the one thing I haven't seen mentioned, or I missed it completely... do you just use the same spring and guiderod that comes in the .40? Is there any difference between the springs in the calibers? From what I'm reading, you are all only buying the 9mm barrel and mags, correct? Thanks for any comments on this.

 

[Smitty357]

I too was just looking at buying the M&P 9mm and then started browsing the forum and read about the .40 conversion to 9mm. So I went to the local gun store and rented the .40 to see how it felt... WOW! It was amazingly accurate and softer than my friend's .40 glock we had with us. So I have decided that's the route I'm going to go, buy the M&P .40 and the aftermarket barrel with 9mm mags.. but the one thing I haven't seen mentioned, or I missed it completely... do you just use the same spring and guiderod that comes in the .40? Is there any difference between the springs in the calibers? From what I'm reading, you are all only buying the 9mm barrel and mags, correct? Thanks for any comments on this.

Just change the barrel, everything else stays the same. Unless of course u also want to use a 9mm mag. The .40 mag will work also with 9mm if u want to save urself a little money.

 

[thedukeoftank]

I too recently purchased a M&P 40 with the intention of having a dual caliber pistol. Everything I have read on the caliber change seems pretty straight forward. The only issue I have seen so far is from a youtube video - Update! M&P40 conversion to M&P9 - YouTube

Looks like a FTE from cheap 115gr FMJ rounds. Now, the main reason I want to do the caliber conversion is the much cheaper ammo. Any ideas on this? One commenter advised changing the recoil spring to a lower lb spring.

 

[mrrstrat]

For what it is worth:

I have an older M&P 40 w/o thumb safety and I bought a S&W brand factory replacement 9mm barrel and some S&W brand 9mm mags for my 9mm conversion.

I found the gun works great as expected with the same accuracy. I shot a bunch of a couple different types of ammo and am convinced I have no issues to expect.

I have heard with the barrel and mag in 9mm the 40 caliber model has the same recoil spring, extractor and spring, striker spring as the M&P 9 so it essentially becomes the M&P 9. I thought I read somewhere the bolt face was also dimensionally the same meaning the slide components are also the same.

Is the bolt face - where the cartridge meets the striker pin - and the place the extractor expects it exactly the same? Maybe someone with both M&P 9 and 40 can speak up.

 

[mrrstrat]

Update: I have ordered the Stormlake 40-to-9 conversion barrel for my M&P 40. I believe this is the agreed proper way as the external dimensions match the 40 correctly. Since safety is number 1 I have to ask: "Is anyone in the market for a slightly used factory 9mm 4.25" barrel?"