.40 slide on 9mm?

[TxAggie]

Hello all, I've been trying to find the answer to this and haven't found it, so I hope this isn't a dupe. I recently purchased the M&P 9mm and chose it over the .40 simply because ammo is cheaper. I didn't realize at the time that you could change out the barrels on a .40 and shoot the 9 as well.

With all the recent scare activity, 9mm has become scarce, but i can find .40 fairly easily So my question is: are the frames in the 9 and 40 the same? If so, would it be possible to just buy a .40 slide/barrel and magazines and still have the ability to fire both ammo?

Thanks for any help.

 

[dfhawkins]

Let me answer it this way. The frame rails and fire controls are the same. However, I would imagine you will find it just as cost effective to buy a new M&P in 40S&W and have two guns. To buy the slide, guide rod/spring, barrel and a couple of 40/357 mags will probably work out to 2/3rds the cost of the complete gun.

 

[Zjnovak]

Let me answer it this way. The frame rails and fire controls are the same. However, I would imagine you will find it just as cost effective to buy a new M&P in 40S&W and have two guns. To buy the slide, guide rod/spring, barrel and a couple of 40/357 mags will probably work out to 2/3rds the cost of the complete gun.

x2. For the compact, the 40 is a little beefier. Just slightly, but there is a small difference. I would assume the same goes for full size, but I only have the 9mm. It may fit, but under much higher pressure you may damage the frame or internals. Buy a used M&P40 if you really want it. I would just hold onto the 9mm and give this whole thing a month or two to settle down. Check with your local walmart every single day for recent shipments on ammo. Stockpile what you can.

 

[shield]

Agree with the others. If you want to swap barrels, you really should have bought a complete 40 and then a 9mm barrel. Going the other way is not worth the trouble and cost.

 

[Smitty357]

Yep, u should have just bought a .40 that way u could swap to .357 or .9mm which ever u prefer at the time.

By the time u buy a new slide and barrel. It would have been cheaper just to buy a .40 to start with.........Or maybe, why not just sell your 9mm and then go buy you a .40. Either way i'm sure its easier and cheaper, IMO anyways.

 

[robkarrob]

I do not agree with the above posts indicating the swap will not work, or would be cost prohibitive. I have a Shield 40 and have a 9mm barrel for it. I have observed that the 9mm barrel and 40 barrels are identical except for the dimension shown on the attached photo. The 40 barrel will fit into the 9mm slide with a minor modification. The area at the top rear of the 40 barrel needs to be reduced (ground down) around .013 inch per side to fit into the 9mm slide. All other outside dimensions on the Shield barrels are the same, except for this small area. Of course they have different bore sizes. There is no reason to believe that other model M&P's are any different that the Shield, model to model. The full size (9 and 40) should be similar and the compacts (9 and 40) should be similar. If you check the parts manual, all parts are interchangeable between the similar sized models, including recoil springs. The only parts that are different are the slides and magazines. The difference in the slides is the 40 or 9mm stamped on them, and the width is different in that area where the 40 barrel needs to be ground down (picture showing .433). On my 40 Shield that width is .433 inch. There is .008 inch clearance between the 40 barrel and the slide. To get the same clearance with the 40 barrel into a 9mm slide, .026 needs to be removed, .013 inch per side, a very small amount. The size of the tang/tab that needs to be ground down is about 1/8 by 3/16 inch. Could be easily ground off using the side of bench grinder wheel or using a hand grinder/dremel.

I am suggesting if you buy a 40 barrel, grind off around .013 per side of the tang/tab at the upper rear of the barrel, you would now have a 40 S&W. Once you've modified the 40 barrel, it would be a drop in conversion. You will need magazines as the 40 cartridges will not load in the 9mm mags. The barrel is around $85 delivered and the mags $30 each.

But honestly to convert the 9mm to 40, because of a shortage in ammo, would not be suggested by me. This ammo shortage will eventually subside somewhat. Those that go from 40 to 9mm are doing so to reduce the cost of practice. You are going the other way, increasing the cost. Unless you really want to to upsize to 40 S&W, don't bother with my suggestion. This post was only to show it can be done.

Bob

 

[TxAggie]

Thanks for all of the feedback, pretty much what I expected. Like I said before, I like the 9 better anyhow, it's just been the availability that had me concerned. 9mm stock is starting to show back up so I'm not AS concerned as before.

If I get a shield in the future, I'll try your .40 suggestion and get a 9 barrel to go with it.

Thanks.

 

[M&P_313]

I have been browsing the web searching for info on this 9 to 40/357 conversion also.. What I'm finding is that the frames are the same, and all frame parts are interchangeable. None of them are beefier on one or the other. The Slide, Barrel, and Mags are the only difference. I've already found my parts and the grand total comes out to $377 w/o shipping calculated. You may be able to find a used M&P .40 or .357sig for $400 in your town, I can't. They run $500 here NIB. Also my M&P is basically bran new 100rds though it yet. My lower end has a trigger job (polishing) and the trigger face is slightly reshaped and smoothed also.

What got me pondering this idea is that I wanted to buy another gun in 357sig or possibly 40. I've tried a few at the range and nothing else really appeals to me. I also don't want an identical gun in just a different caliber. So I've been considering a Glock 29 10mm which can shoot 5 different cartridges including .40 and .357sig with conversion barrels, that gives me alot to play with So far the cost of converting my 9 to a .357 is not sounding bad though..

M&P .357 compact slide (stock sights) $200.99 ~Midwayusa
M&P .357 stormlake barrel $150.00 (you may be able to save $$ here with a different option)
M&P .40/357 Magazine $26.00 ~ProMagindustries
If you think you'll need a new spring rate for this kind of conversion, gunsprings.com has them for a whole $7.89 ranging from 12-24lbs

 

[DocSunShine]

Storm lake makes a 9mm to .40 conversion barrel. That plus .40 mags will get you converted to a .40. No new slide required.

StormLake | Build Your Barrel

check again, it's a .40 to 9mm conversion barrel, but the wording is a bit confusing.

 

[JFR]

check again, it's a .40 to 9mm conversion barrel, but the wording is a bit confusing.

Brain fart. You are correct I forgot that you can't go 9 to 40 without the slide. Thanks

 

[DocSunShine]

Brain fart. You are correct I forgot that you can't go 9 to 40 without the slide. Thanks

Had I looked quickly and didn't already know they weren't available I would have thought the same based on the wording.

OP like Rob said, you can modify a .40 barrel to fit a 9mm, but it simply makes more sense to buy a .40 first and get conversion barrels. That's kinda why I own .40s, I took note during the last panic, .40 was the last caliber standing you could find. I do like the increased barrier penetration abilities of the .40 but I'd be perfectly content carrying a 9mm, 6 in one and half a dozen in the other for me.

Honestly if it were my 9mm M&P I'd seriously sell it (but keep any and all extra mags you have), buy a .40 and get a 9mm conversion barrel. That simply makes the most sense. Now if you were to do that, take a look at the thread I started about 9mm conversions with the green recoil spring. Previously the extractor, ejector and recoil spring were all the same with 9mm and .40 so the conversion was seamless, but now Smith is using a slightly heavier green spring (used to be used in the .357 sigs) in the .40s and I suspect this might cause some issues with 9mm, but the good news is blue recoil springs can be had an for cheap, just keep this in mind.

 

[JFR]

Honestly if it were my 9mm M&P I'd seriously sell it (but keep any and all extra mags you have), buy a .40 and get a 9mm conversion barrel. That simply makes the most sense. Now if you were to do that, take a look at the thread I started about 9mm conversions with the green recoil spring. Previously the extractor, ejector and recoil spring were all the same with 9mm and .40 so the conversion was seamless, but now Smith is using a slightly heavier green spring (used to be used in the .357 sigs) in the .40s and I suspect this might cause some issues with 9mm, but the good news is blue recoil springs can be had an for cheap, just keep this in mind.

I was going to suggest the same thing as well. As another plus on this suggestion, and depending on how old the 9mm is, you would most likely buy a new .40 with all of the recent production upgrades to the trigger.