Hi, I seen a couple posts pertaining to the fact that you can convert a 40 S&W to 9mm by changing out the barrel..So now I am thinking this may be a good option as I've never had or shot 9mm. So anyway looking for some help..
What are the advantages for getting a 9mm? Also I see the Barrels from Storm Lake are $150 or more..Are there alternatives? Seems like if I spend this much for barrel and then what about a new 9mm magazine or two..I am looking at a good amount of money that could go towards a whole new gun??
Please point me in the right direction..Thanks!

I used S&W OEM 9mm, 40 on my .357 MPC all works well. Not sure it you are able to purchase them anymore but it was very cost effective. Yes you need replace magazines but that is very low cost.

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I got a factory 9mm barrel for my full sized .40S&W. I then found two 9mm mags and I was in business. I think it would be worthwhile to replace the recoil spring as well because the ejection is a little weak when shooting 9mm. Even so, the gun works as a 9mm.

I got a factory barrel from Midway USA for about $70. I got the mags used for about $40. So, for about $110 I have a new gun.

The question now is, is it worthwhile to do it? Well, if you want a 9mm this is the least expensive way to get a good one. That said, there's nothing wrong with the .40S&W round. 9mm is a little less expensive to shoot. That's the only real benefit to switching to 9mm.

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Thanks..that would be about half the cost and would seem more sensible (unfortunately checked Midway and out of stock/no back order)..
I would certainly be tempted to give 9mm a try for that cost..Anyone know any vendors that have them in stock?
Why are the conversion barrels so much more?

Even if you went with the $150 conversion, you can get mags from Quantico for 29.95 each, or 3 for 78.00, and have an M&P FS 9mm for about 250.00. If you're just looking to save on ammo, that would take a while to recoop, but if you want a 9mm, just to have a 9mm, then you're not going to find a better gun at a better price than that.

S&W M&P 9mm Full Size Barrel at G and R Tactical

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Out of curiosity, if you already have a 9mm M&P, can you do a 40 S&W barrel/mag change with same results? or would you also need to change out recoil spring too? Thinking it might be beneficial to be able to convert from one caliber to another, if ammo becomes hard to find again.

Will the conversion be as accurate?

Yes, has anybody done this?

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Thanks for the link! Unfortunaty when I tried to place order from cart it showed unavailable and no back order..
Anyway, has anyone had a chance to compare both options? I can get the conversion for $150 with free shipping,, the one in your link was $99 plus shipping cost... so about. $40 difference. Not a lot if the quality and fit is better.
I still like the sounds of Midway though ( around $75.00).. But if not available then, I guess not an option

Looks like you can convert the 40 S&W version to three different rounds in one pistol easily. Looks good to me. Easier to find ammo that will work.

Might have to look into this.

Give them a call, their online ordering system is flakey . I didn't do a .40 to 9mm conversion but I did put a KKM replacement barrel in my 5" Core. I didn't notice any improvement in accuracy and speed, but I don't shoot heavier bullets (over 130gr) so I wasn't expecting much difference. HTH

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You can't do it IIRC. The breach face on the 9mm slide is too small to fire the larger 40 cartridge.

Actually, it can be done, but it's not as easy. Jiman is correct and the breech face on the 9mm slide is a little smaller than the .40S&W is. If you get a .40S&W barrel, the sides of the hood can be filed down a little and it will then fit.

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Call S&W to see if they have any in stock. I've have had a 9c barrel on back order with Midway for months and was getting tired of waiting so I called S&W. They had some in stock for $72 so I ordered one. I don't know if they have the FS 9mm barrels but it's worth a phone call.
This was last week.
We have 9mm barrels for all of our M&P 40s. When I take new people shooting I start them off with our M&P 22 then move them up to the 9mm. It's a good progression for newbies.

I've got the .40 to 9mm conversion barrel from KKM Precision and it works great in my 40c. I know it'll take me a long time to make up the cost by the savings in ammo, but my wife and I are learning to shoot semis and I thought the 9 would be easier to learn with than the 40.

I got a 9mm barrel from Midway yesterday that has been on backorder for right at a year. I already have a full-size 9mm magazine that I use for my 9C with an X-Grip. Haven't had a chance to use them yet, but I'm looking forward to giving them a test drive tomorrow.

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M&PC FS BG Shield+ 642 686+

I think the biggest advantage of a barrel swap vs getting a new gun, is that all the mods, and tweaks carry over. You have the same trigger, sights, and feel...not to mention all the $$$ you'd have to spend in aftermarket part if you got a new gun.

If you own a 100% stock gun, it might be cost effective to get a whole new gun.

Or if you have an M&P40 with the Apex FSS kit, you can see what an M&P9 with an FSS kit would shoot like.

If you reload, a 180g 40 S&W bullet with 3.0g Red Dot or Clays will let you know what an M&P9 feels like with 1100 fps 120g bullets at an even lower cost.

Thanks for the response. I'm not interested in "making" my 9mm work with a 40 cal. barrel, especially having to file things to get them to fit. I was just curious

Seems to me, S&W would put together a combo set, pre-packaged with a frame and the 40, 9mm and 357 Sig barrels/mags for purchase; kind of like a Dan Wesson kit, but to change calibers, not barrel lengths. Just a thought....

While it might seem to make sense, it's more complicated than it appears.

Remember how I said that the .40S&W barrel hood would have to be filed down to fit the 9mm slide? Well, that means the 9mm barrel hood doesn't fit the .40S&W slide well; it's a little loose. This means that a .40S&W gun, converted to 9mm, is not as good as it could be. So, a .40S&W barrel, fitted to a 9mm slide will actually be a better conversion. This is also why an after market .40S&W to 9mm conversion barrel is better than just dropping in a factory 9mm barrel.

Now, that all depends on what you want for precision. I can testify that the factory 9mm barrel works in a .40S&W slide because I have one. I have not tested it to see just how precise it is. I only know that it's good enough to use as a defensive gun which is to say not very precise.

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The differences between the three calibers, in the way they fit in the slide are so minor that if S&W wanted to make a combo kit they could easily do it. The retail price on the other hand might make that multi caliber kit way more expensive than most people would be willing to pay. I'm sure it would be much more expensive than the cost of a barrel and a couple of mags.
As Rastoff stated, I'm satisfied with the accuracy of a factory barrel in my 40s.

Did not know that. Thanks for the info. I was always under the impression the factory barrel was best.

At the risk of asking a hijack question, which brand of conversion barrel would you suggest?

I have my M&P CORE in 40s&w. Bought a KKM 9mm barrel. Two 9mm mags from Greg Cote,LLC . The gun is very accurate with the 9mm barrel. It works out great when you need ammo that you can use 40s&w or 9mm.

I cannot suggest a brand. I only know that they will fit better due to the design. I have not used any conversion other than to put the factory 9mm in my .40S&W gun. Since I have no personal experience, I cannot in good conscience make a recommendation.

Again, I can only say that the factory barrel is adequate for defensive accuracy. I haven't shot mine further than 10 yards.

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I have shot my FS and compact 9mm barrels in my .40s at 15 yards and shoot them the same as the factory 40 barrels. I'm not a great shot but my accuracy is the same. Good enough for personal defense.

The POI can vary when using the different barrels. When shooting close range the variance will be much less, but will increase as the distance increases. I have a Shield 40 and when I use a stock 9mm barrel, the POI ends up being 2 inches lower and 2.5 inches further right at 15 yards, compared to the POI using the 40 barrel. The 40 and 9mm groupings both remain in a 2.5 inch circle. Since I carry as a 40, I keep the sights aligned to the 40 barrel. I use the 9mm only for practice, for less expensive ammunition and less recoil. If I am shooting for accuracy with the 9mm, then I expect the POI to be right and lower. I always practice with some 40 practice and SD ammunition, just to keep the different recoil and flip ingrained into my shooting.

I bought some 9mm mags to use with the 9mm barrel, but I found my 40 mags feed the 9mm ammo perfectly. Some have said they have feeding problems with the last 9mm round, when using the 40 mags, but I do not have that problem. I would think the feeding problems is caused by slight differences in the width of the mag feed lip.

Bob

Last spring I gave S&W customer service a call inquiring about 9MM and/or .357 SIG barrels for my 40C & full size 40 & I was told that they were unavailable. I asked what his best guess when availability would be & he said probably never. I always meant to call them back & ask the same questions.

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Just to follow up, word from the North Pole is I'll be having a Storm Lake conversion barrel and 9mm magazine in my Christmas stocking ;0)
I've been getting more and more excited about having this option with my M&P since first posting..really didn't have any extra money as I recently purchased a new hunting rifle in mid October..
Stoked

I put the Storm Lake 9mm conversion barrel in my .40 Core. It shot good but I had 1 FF and my wife had about 10. I'm thinking recoil spring assembly? Gun shot great, felt great! I really want to fix this as soon as possible anyone know what weight spring I should be running for the 9? Ammo was Magtech 115 gr FMJ ran flawless in my Glock 17 & 19 and Shield.

I posted above that I called S&W to see if M&P 9c barrels were available and I was able to order one. Earlier this week I called the check on that order as they never sent any order confirmation. I explained what was going on to the S&W rep who was very surprised that I was sold a barrel. I gave her my order #, she put me on hold for a really long time then came back and told me that they do not sell barrels to the end user. The reason she gave me was...they don't was people to put 9mm barrels in .40 cal slides. Then told me that my order will not be filled. Well, today I checked my bank statement and a charge for $82.42 from...you guessed it, S&W. I'll keep you posted if/when I receive it. If it shipped yesterday or today I should get it before the end of the year. No need to even think about calling S&W as they take the next two weeks off.

OK, checked the mail box today and there was a small package from S&W. Inside, a 9c barrel. So I guess it just depends on which customer service rep you speak to when you call.
I was surprised though. It shipped from Kentucky. Maybe the factory that makes the barrels is there.

I had a similar experience. I took my neighbor and his sons to the range and ran some 9mm through my 40 with StormLake conversion barrel. It seems to go ok for a while, then starts to have failures to feed and failures to eject.

The part numbers for 40 and 9mm guide rod spring are the same, but my 40 works flawlessly with 40 ammo and the factory barrel.

Below is an after-the-fact recreation of what the failure to eject looked like.

Attached Images

20141224_131244_400.jpg (34.2 KB, 474 views)

Do the failures to eject happen when you are shooting or just when your neighbor is shooting? If it only happens when your neighbors are shooting it might be technique. Just a thought.

Interesting. I've never had anything like that happen with the KKM conversion barrel but I doubt that it has anything to do with the barrel. The extractor and ejector are the same on the 40 and the 9 so it would seem that the only thing it could be is the slide not going far enough to the rear for the spent round to engage the ejector, no?
Does it do that will different brands of ammo? What are you shooting and what weight projectile?

If it just happened with the neighbor it could be not locking the wrist which take the blunt of the recoil.

It only happened when the neighbors were shooting, so it could be related to how they are holding it. But, they all had zero issues with the M&P Shield 9mm.

The rounds I used (without issue): Winchester Nato FMJ 124 gr, 1200 fps, 396 ft-lb.
The rounds they used: Fiocchi FMJ 115 gr, 1250 fps, 400 ft-lb.

I guess I just have to go back to the range again....purely scientific curiosity, of course.

Edited to remove erroneous info.

Now, using a proper/stronger grip masks potential issues. A weaker/improper grip will expose small weaknesses in design. If you swap out the recoil spring with a 9mm weight spring, I'll bet the problems go away.

When I shoot my .40S&W with the 9mm barrel in it, the ejection is weak. I've never had an issue, but then my grip is solid. I'll bet it could be an issue if I were to hold it differently. Hmmm, maybe I should do some experimentation as well. Ah, being forced to go to the range is such a chore, isn't it?

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Where can the 9mm recoil spring be purchased? I've only seen the recoil spring that is suppose to work in 9, 40 and 357 sig. I haven't had an issue but after shooting for a while my wife starts having FTE problems. I take it as a sign she's getting tired and it's time to stop.

There are a bunch here: Springs : Welcome to Speed Shooter Specialties

You can also call S&W and see if they'll sell you one.

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I'm looking for the factory spring. I haven't seen any factory springs specific to the 9mm. I might just call S&W to see if they will sell one.

Ras
I believe the recoil spring assembly is the same in the 9c and 40c.
Is that correct?

Edited to remove erroneous info.

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I'm going to cover several issues mentioned above:

1. The recoil spring on the full size M&P is the same for 9mm/.40 S&W/ .357 Sig because the SLIDES ARE DIFFERENT. If you look closely, the 9mm slide has lightening cuts forward of the ejection port that aren't in the .40/.357 slide. The only difference between the .40 & .357 slide is the roll mark for caliber.

BTW, S&W informed our lead armorer that the paint codes on recoil spring assemblies is for internal (to the factory) parts ID, has nothing to do with tension ratings. We assume they refer to source of the parts, they didn't explain further.

2. Since the 9mm slide is lighter than the slide of the .40 slide, swapping a .40/.357 barrel in may result in excessive slide velocities. This can result in frame damage and other ill effects.

Looking at a much earlier situation with the 1911, there was a great deal of dimensional overlap between the breech faces of a 9mm and .38 Super. It was/is eminently practical and safe to use either barrel with either slide. There's also enough overlap in extractor dimensions that there's no significant difference there either. That's not necessarily the case with the M&P.

In 50+ years involved with firearms, I've seen a number of demonstrations that there may in fact be a Supreme Being who sometimes takes care of fools and little children. Just because it may be possible to do something does not mean it's a good idea. FWIW, my personal opinion is that if you're up for switch barrels on an M&P, get a purpose made conversion barrel from the folks who make them.

Given the (apparent) different slide weights, I'd like to see some slide velocity numbers from someone like HP White before I'd think about trying to shoot .40 from a 9mm slide. OK, I'm cautious. It's how I got to be a senior citizen.

Interesting info. It doesn't answer the question of why 9mm has one color and the .40 has another, but it's as reasonable as any speculation I've seen. Since I don't have both recoil assemblies, I can't measure their tension.

It makes at least some sense that these are just internal factory identifiers like the dimples on the chamber.

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This is great information

If I read this right - my GF can get a 9mm barrel and shoot 9 mm out of her MP 40 I knew you could do that with the 357 Sig but not the 9mm

It also might ID M&P recoil assemblies from Sigmas and whatever else might look similar. All they said was internal ID.

We asked after seeing blue paint on the original assemblies and spare parts came with some other color. Yellow? Several years ago.

Great info, thanks. Mine does indeed have the green paint. I will see about getting a softer spring - more for completeness than anything else.

I retract my earlier statement. Apparently my info was wrong. So, I'll go back and edit my post.

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Thanks for the follow-up.

From gunsprings.com, I see the following:

•Reduced Power.......: 12, 14 & 15 Lb.
•Factory Standard.....: 16 Lb.
•Extra Power............: 17, 19, 20, 22 & 24 Lb

So I take it, I could go with a 14 or 15 lb replacement while using 9mm.

Here is the link:

Springs for SMITH & WESSON M&P SERIES - 9mm, .40/.357 Semi-Auto Pistols