Questions on M&P40c conversion to 9mm

gun1 · Feb 28, 2013

I have done some research and my understanding is that the factory 9c barrel will work in the 40c, along with the 9mm mags as there have been feeding issues with the 40/357 mags running 9mm.

My first question is in regards to the barrel. If a 9c can't be converted to a 40c because the 40c barrel is too big to fit through the hole in the front of the slide, than would a 9c barrel not have too much clearance in the hole on the front of the slide of a 40c? It just doesn't make sense to me that a factory 9c barrel, being a smaller diameter, would work well with a frame designed for the larger 40c barrel???

Second question: why are the Storm Lake conversion barrels so prone to jams? Is it the design of the guide ramp in to the chamber in that there isn't enough clearance between the tip of the round and the top of the chamber? Has anyone modified one to cure the jamming issue (such as taking a round file, or grinder of some type, and knocking down the top of the ramp a few thousandth's [.001"s])?

gun1 · Mar 2, 2013

I have access to a 9c today, so Ill play around with the components - and take pictures

As it looks, best I can tell, the 9c barrel is able to move in the breech side to side, just a hair, but it may be too much, with the slide in the firing position (breech closed).

MSG Glenn · Mar 2, 2013

The 40C can also take a .357SIG barrel. It doesn't require a separate mag because the .40 & .357SIG use the same one. Some have used the .40 cal mags with a 9MM conversion but only for range fire & definitely not for self defense EDC. There can be an occasional misfeed problem.

I've never heard of anyone having problems with factory original S&W 9MM or .357SIG barrels in a 40C.

seattle911 · Mar 2, 2013

gun1 said:
Second question: why are the Storm Lake conversion barrels so prone to jams? Is it the design of the guide ramp in to the chamber in that there isn't enough clearance between the tip of the round and the top of the chamber? Has anyone modified one to cure the jamming issue (such as taking a round file, or grinder of some type, and knocking down the top of the ramp a few thousandth's [.001"s])?

I am not sure where you heard that but my SL conversion in a 40C has been as reliable (100%) as the factory 40 barrel.

gun1 · Mar 2, 2013

OK, so here is my picture set.

This is the slide with the 9c barrel:

Before I get in to the fit with the 9c barrel here are a couple shots of the fit with the 40c barrel:

Note the amount of light:

Now here is the 9c barrel fit. Note there are two top pictures - look at the loaded chamber indicator and the orientation of the barrel to it, as well as the space on the sides between the barrel and the slide directly around the loaded chamber indicator:

Then here is the bottom. Again, note the amount of light.

The long and short of it is there is some play in the 9c barrel. I wish I had my micrometer and calibers with me this weekend because I'd get you guys the exact dimensions and clearances. In any event, the pictures are decent.

We're hitting the range tomorrow. If I get a chance to swap the barrels and test the set up I will and report back.

gun1

dfhawkins · Mar 2, 2013

gun1,
This issue has been on the forum for a long time. Yes it can be done (Personal experience with Full size, Compact, and Shield). The magazines are more effective if they are specific to the caliber (40/357sig or 9mm) and the space on the "ears" on the top of the barrel for the 9mm bbl in the .40 slide is a non-issue. I expect you will be posting a successful experience at the range.

Check out posts on this subject by lostlake, smitty357, and robkarob. They have done the research and experimentation!

robrossk · Mar 2, 2013

My FS 40 works just fine wih the 9mm and the 357 sig barrel - no issues to report

CJ_mp40c · Mar 3, 2013

So I have heard that the .40 can be converted into a 9mm (and 357sig). But the 9mm can't be converted into a .40 or a 357sig.

Disclaimer: I'm not stating anything other than measurements taken on my two guns (full size 9mm and a compact .40).
These measurements were taken, using a digital micrometer.

Barrel outside diameter at the muzzle, 9mm- .563
Barrel outside diameter at the muzzle, .40- .5635
Breach outside width, 9mm- .592
Breach outside width, .40- .592

I wonder why you can go .40 to 9mm but not the other way.
Also (when looking at the storm lake website) they sell .40 & 9 barrels but also sell conversion barrels. What is the difference?

robkarrob · Mar 3, 2013

The 9mm to 40 can easily be done, and has recently been done by a member. It is not a drop in barrel conversion like 40 to 9mm. But it takes just a little grinding on the 40 barrel tang, to get the 40 barrel to fit into the 9mm slide. Start at post #110 and you will see it works. If you go back to post #65, it shows what needed to be done. You will also see there is always someone posting that it won't work, is dangerous, etc. Well I can tell you there are always someone that wants to convince everyone else to not make changes to their guns. They want to push their viewpoint, whether correct or not. In that forum all the negative viewpoints were proven to be wrong.

Bob

http://smith-wessonforum.com/smith-wesson-m-p-pistols/280665-converted-my-shield-40-9mm-3.html

Robotech · Mar 3, 2013

It's not just the barrel tang that would need to be modified, but at least on my FS 9mm, you'd have to widen the breech-face on the slide to accommodate the slightly wider .40 shell. (This may not hold true on the Shield, but is definitely the case on my FS M&P9.)

If you need to up-convert from a 9mm to a .40S&W, I recommend just getting a 40 slide and barrel. If you want to do it a little cheaper, get a stripped slide and barrel, and transfer the rest of the parts from the 9mm slide.

gun1 · Mar 3, 2013

I didn't have a chance to shoot the 9mm barrel today. The day just flew by and we didn't have time.

I did try to put the 40c barrel in the 9c slide yesterday and it does not work.

My guess is the accuracy with the 9c barrel in the 40c slide is not as good because there is a little more slop in the fit.

CJ_mp40c · Mar 3, 2013

gun1 said:
I didn't have a chance to shoot the 9mm barrel today. The day just flew by and we didn't have time.

I did try to put the 40c barrel in the 9c slide yesterday and it does not work.

My guess is the accuracy with the 9c barrel in the 40c slide is not as good because there is a little more slop in the fit.

robkarrob said:
You are correct, it is the proper length. You wouldn't want to try putting a 9c barrel into a 40fs. Swap model to model:

Shield 40 with a Shield 9mm barrel
M&P 40c with a 9c barrel
M&P 40fs with a 9fs barrel.

If you are referring to the differences in the barrels, check this photo out, which shows the tang width differences.

Bob

This is from another thread http://smith-wessonforum.com/smith-...lake-9mm-conversion-barrel.html#post137061759
It shows the differences.

Questions on M&P40c conversion to 9mm

gun1

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gun1

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MSG Glenn

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seattle911

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gun1

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dfhawkins

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robrossk

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CJ_mp40c

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robkarrob

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Robotech

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gun1

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CJ_mp40c

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