Test-9mm factory barrel in M&P 40-

[BigRich315]

The benefit of an aftermarket conversion barrel like Storm Lake is that it is made to the dimensions of the factory .40 barrel, the only modification being the bore. You can see the obvious differences in the two factory barrels, and as always, YMMV. What works for one gun may not for another, there can always be minute variances.

My 40/9c has worked flawlessly with the Storm Lake barrel. To me, that assurance is well worth the little extra $$.

 

[bronco57]

In order to prevent the slide from holding up on the magazine, could you change out the plastic magazine follower in your magazine to one that initially fits 9mm rounds? I am assuming the metal part of the magazine is made to the same dimensions for 9, 357, and 40 calibers.

Also, does anyone have pictures of what the gun looks like with a stainless barrel as apposed to the standard black finished barrel that comes stock from smith?

 

[Robotech]

The feed lips on the .40/357 magazine are slightly farther apart than on the 9mm. (Just checked that today when I finally got hold of a .40 mag.) Whether that's enough to cause a potential problem feeding, I don't know.

I'd suggest using the correct mag for the caliber if at all possible. Yeah, I KNOW they're hard to find. I'm guessing the only reason the store I found one at today had a few 40s was that they'd jacked the price way up. They were out of the 9mm. (But at least I'll be able to shoot the 40 once I finish assembling the new slide and barrel.)
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Just did a quick check. I'd have to say DON'T try to run 9mm out of the .40 mag even with the 9mm follower. The 9mm rounds ride high and are barely retained, tilting upward at the front, which is also why the follower comes up so high with one round remaining. And if you try to put .40S&W in the 9mm mag, at least with what I have, the bullet case tends to catch on the front edge of the magazine.

 

[bronco57]

Thanks Robotech. I was curious if that would work. Too bad it doesn't because swapping out the plastic magazine follower would be a $4 solution and not have your name on a 6 month waiting list!

 

[ATGglobal]

I would really like to know if the 40 barrel will fit the 9mm slide. Who has both and can try? That would be too cool.

Not sure if this has been completely answered. A .40 barrel will not lock up in a 9mm slide since the ejection port on the 9mm slide is actually smaller than that of the .40S&W slide. Some people have suggested you can trim some of the barrel hood off the .40 barrel to make it fit but you wouldn't be able to use it in a .40 slide. Also if you trim too much off then you just scrapped the barrel.

I want to bump this back to the top to find out anything new on these 9mm conversions with oem barrels & ask if anyone else has tried this with the M&P 40 pro 5" barrel. Also would like to know what the reliability of the 9mm barrel in the 40s&w is turning out to be. I want a target pistol in 9mm that I can also use as a HD pistol in 357sig & 40s&w. If the 5" oem barrels swap the same way as the compacts seem to do then this is the answer. If not I will be buying the Glock 35 which has many conversion options awaiting me after purchasing it. I am totally intrigued with this 9mm OEM barrel conversion drop in concept.

I had a few ejection problems while running a 9mm barrel in a .40 slide, which is why I don't recommend it for carry. I think it might have to do with the breach face and extractor tuning. I know a 9mm slide would alleviate the problem completely, but I also hear the "conversion" barrels do too simply because they actually slightly shift the location of the 9mm round higher into the breach face for a positive interaction with the extractor.

 

[Smitty357]

Not sure if this has been completely answered. A .40 barrel will not lock up in a 9mm slide since the ejection port on the 9mm slide is actually smaller than that of the .40S&W slide. Some people have suggested you can trim some of the barrel hood off the .40 barrel to make it fit but you wouldn't be able to use it in a .40 slide. Also if you trim too much off then you just scrapped the barrel.

I believe u are over looking something here. A few members have successfully trimmed the .40 "tangs" down on their barrel to make it fit in the 9mm slide (of course this was with the Shield also). After those "tangs" are trimmed down, the .40 barrel is pretty much the same as the 9mm barrel. Which is why the .40 barrel then fits into the 9mm slide...........Now we also know the 9mm barrel drops into the .40 slide and works perfect. So since this .40 barrel is now the same size as the 9mm barrel. We also know it'll drop right back into the .40 slide. Of course the tangs on the .40 barrel are a very very tiny bit smaller than it was before. But it fits just fine and is basically like dropping a 9mm barrel into the .40 frame.............Once again, this is with the Shield. The FS could be a different weapon.

 

[Georgia Yankee]

The barrel extension is indeed narrower on the 9c barrel than the 40c. It is visibly narrower, maybe .030 or .040 or so (I have not measured, but have observed the two side-by-side.) Others' experience indicates a 9mm barrel will work in the 40 slide, but one might expect some loss of accuracy as the rear of the barrel floats from side to side a few thousandths, and possibly unreliable ejection as the wider breech face may engage the 9mm case less securely. I have back ordered a S&W 9c barrel for my 40c from Midway for $65. I could try peening it or stippling it to widen the barrel extension, but that would not be without risk; if it shoots well, I will leave it as-is. I'll let you know how it goes, but it might take months to get it.

 

[Richie15]

I just - last week - put a 9C slide and barrel on top of a 40C frame, and the 40C slide and barrel on top of a 9C frame....

(Of course, I had all the necessary magazines.)

Worked fine.... Dimensions ought to be about exactly the same - or at least within tolerances. It appears that the guns are identical except for the breech face and the bore size.

The reason? The 9C came through with a thumb safety, and I'm a 1911 guy, so I decided that I wanted that on the 40C I carry around the house. I was a little concerned - the sear block on the 9C has a headed sear pin, and the ejector is a little different, but everything worked. I was prepared to swap sear blocks and figure out how to install the thumb safety in the one from the 40C, but it wasn't necessary.

(FWIW, I, too, find the thumb safety kind of silly on this gun, but I'm used to it, and I didn't want it on the 9C. That one's supposed to go to my daughter if she doesn't stay in New York.... My problem is that I think it'll turn itself ON on it's own, and if you're not used to it - there's really no need to leave it on - you've got a problem. Since I'm used to a thumb safety, no problem.)

One funny result. The 9C tended to toss empties up over my head, while the 40C sent them off to the right. Now they both seem to toss 'em over my head ....

Someday....

It appears that the .357Sig barrel is all you need for that conversion, btw. The magazines are compatible. Haven't tried it. (Can't think of a good reason, but that's another thread.)

The .45 versions are NOT the same sizes, AFAIK. I don't think you can put a Compact slide on a Full Size frame, either, although....

Regards,

Hey I know this thread is old but did you use .40 mags in the 9c

 

[oworthsr]

I know from experience that a 357Sig barrel will work straight away in a 40 or visa-versa. I'm pretty sure a 9mm barrel will work in a 357 M&P with the 9mm Magazine and possibly a 9mm recoil spring. Bob

I agree. Earlier this year KKM Precision built and sold to me their .40-to-.357Sig conversion barrel (4") for the M&P 2.0 and it works just fine.

I recently checked their website and discovered that KKM also makes and sells their .40-to-9mm conversion barrel for the M&P 2.0. Here's the link: M&P Compact 2.0 40S&W to 9MM (4.0″ Model) | KKM

Email from KKM confirms this is a drop-in barrel - no fitting needed. Just drop in the barrel and use 9mm magazines.

I'm buying one of the .40-to-9mm barrels so I'll have all three calibers covered with one chassis.

 

[Racer X]

The benefit of an aftermarket conversion barrel like Storm Lake is that it is made to the dimensions of the factory .40 barrel, the only modification being the bore. You can see the obvious differences in the two factory barrels, and as always, YMMV. What works for one gun may not for another, there can always be minute variances.

My 40/9c has worked flawlessly with the Storm Lake barrel. To me, that assurance is well worth the little extra $$.

with the 9mm in a 357/40 slide conversion barrels, they typically offset everything .022" ish to the right on the barrel blank to properly bring the case head under the extractor hook. You wouldn't see this by eye most likely.