A while back I decided, perhaps logically or not, that I wanted a 9mm revolver for carry. I went back and forth a bunch on practical advantages/drawbacks and finally said what the hell I'm doing it.
I have a M&P340 and shipped it off to get a 9mm conversion from mark at pinnacle performance. He was super easy to deal with and I'd recommend him based on this and the work done. Some time later it's back. The machining is precise and it works well with S&W moon clips. I haven't notice any problems whatsoever.

At the range it shoots to point of aim, recoil is manageable and moon clip reloads are as fast as anyting out there. I've probably put 1-200 rounds through it since it's return and I'm happy. It's not ground breakingly different from 38+p, but it does recoil less than 357 for sure. Mostly it's fun. And I like the idea of having a BUG in a caliber that i otherwise carry. 'Tis more of an academic consideration in reality because it's doesn't headspace w/o a moon clip. Who's gonna load a moon clip under duress? Not me I hope.

It carries superbly. 1 lb 0.1oz loaded w/ 147HP, and 1lb 3oz in desantis leather. I can just about forget it's there. Not that's a new concept here, but a J-frame just carries well. The cylinder sitting at about belt height seems to tuck it into my gut and hide the grip but it's still easy to draw and offers a good hold.

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Just what all was involved in the conversion? New barrel? Or use the old one? I admit that this is something of a novelty to me. I have a M&P 340, and not sure that this would appeal to me or not, but just interested in the mechanics...is the barrel still stamped with the original caliber?

Best Regards, Les

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SWCA 3084, SWHF 495, PGCA 3064

Yeah can you still fire 38/357 in it with and without moon clips
would be nice to have a 3 caliber gun

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John Hermesmeyer USMC9296

The gun is still stamped 357. No barrel swap the 9mm 38/357 bullet is pretty much the same, might be .001-2 off but accuracy is good and no reports of saftey issues. This is well documented and lots of "conversions" have been done. The body of the gun/ barrel is unchanged. Only the cylinder and extractor need to modified. The pic of the cylinder face shows where it was recessed to accept moon clips. The cylinders are also modified, in this case they accept put to 9x21mm which is an odd-ball cartridge but tis what it is, maybe i'll play with it someday. As is it'll shoot 9mm 38 357 and possibly others...9x21 9x18? I'm not 100% but Mark would know. For me it handles 9/38/357 and that's all i plan on. The conversion wasn't cheap at $225ish but not crazy expensive either. I got my moneys worth. Given the cost differential b/w 9 and 38sp it'll pay for itself at some point, but that was a peripheral consideration for me.

OK, since I know nothing about this subject, let me ask you a question. I also have a 640-1 chambered for .357, and cut for moon clips. Obviously I could carry both .357 or .38 Spl In it either with or without moon clips. Would it also accept 9mm in a moon clip? Or would it have to be further modified?? Just curious, and I don't have it with me right now, or would probably just see if it would fit.

Does yours accept .357 in moon clips?

Best Regards Les

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SWCA 3084, SWHF 495, PGCA 3064

What in the world grips are those?

And so you shoot 9mm, 38 special, AND .357 out of only one cylinder?

You can shoot 9/38/357 at anytime. 38/357 will space w/o moon clips due to the rimmed cartridge. Moon clips can be used if you'd like. Presumably some cartridges/mfg might have issues due to firing pin length/strike and the slight removal of cylinder to accommodate the moon clip. I have not encountered this but it might be the case. No pun intended.

An unmodifiec 38/357 cylinder will not accept 9mm rounds. They simply wont fit. I don't know specifics but the cylinders are machined/enlarged in some way to accept the 9mm rounds. I can now drop a 9mm and it sinks all the way past the rim. 38 still catches b/c of the rim. My reading (the guys who machine these) suggests that shooting 38/357 may lead to sticking cases as they expand slightly. In my shooting this wasn't dramatic but I mostly shot 9mm, the 38/357 i shot worked but did eject a touch harder.

Pics show a 9mm round in a 38spl, then the same round in the machined 9mm gun, and finally a 38spl in the 9mm machined cylinder.

FWIW I found 2 companies i thought would do a good job. Mark at pinnacle high performance (who did my cylinder) and TK custom. Both can be found with a google search and I have no affiliation to either.

The grips are houge tamers that I trimmed down. They are great at absorbing recoil and short as the frame for concealment. For me they are the perfect set up.

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Looks awesome! What tools did you use and can you post other pictures showing what you did?

Here's a link to an older thread on the grips. I didn't look it over but I think the cut/grind process is mostly there. If not I can update.

Houge Tamer "boot grips", modded for concealment

May have to buy once cry once and then buy some more and cry some more

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John Hermesmeyer USMC9296

I'm a little late to this thread but it looks like your gun came out great, your experience with Mark's work and his 9mm J frame conversion mirrors mine, though he did my 360J 8+ years ago.

I can clarify a couple of things. Unless he has changed how he does it, Mark cuts the chambers to 9x23 dimensions. Your cylinder should now shoot not only 9mm (9x19) but also 9x21, .38ACP. .38 Super, 9mm Largo, 356TSW, 9x23 Winchester (I don't recommend that, it's wicked nasty), etc.. Because the chambers are now larger diameter at the base and tapered .38spl cases can swell and stick, .38spl +P and .357mag can swell to the point of splitting so you want to avoid them. If you want to be able to shoot .38spl/.357mag you can source a cylinder and have Mark fit it to your gun to make it a convertible. That is what I did, I bought a titanium .38spl cyl from Numrich's about 5 years ago, finally got around to sending the gun back to Mark last year and had him fit the new cylinder to it. Now switching from the modified 9mm cylinder to .38spl is as easy as slipping one cyl off the crane and sliding the other on.

As far as accuracy and the .357 barrel vs .355 projectiles, that .002" is a much bigger deal in discussion than it is in reality. Like cleans up's gun, mine shoots as well with 9mm as it did originally with .38spl. I have used it to win an IDPA BUG match and haven't had any trouble qualifying with it on the duty weapon course of fire. In the years that I've been carrying and shooting it I haven't found a downside to the mods or regretted my decision.

cleans up - Keep us posted on how the gun performs for you!


Here is a pic of mine with both cyls-

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Don't kiss smiling dogs!

Still wishing ( probably no way due to the way they only seem to release new guns in stainless which I hate) s&Wwould do a 919 ( 6 shot blued k frame in 9mm) and design it so it would work with or without moon clips

I always thought that S&W ending production of J framed 9mms was premature. Prices on used ones are over the moon.
I have 2 9mm S&W revolvers. A 940 no dash and a 940-1. Both are easy to carry but they're really whippy, but I love the 9mm S&W revolver concept. Both have the Uncle Mike's boot grips. I may try a set of modified Hogue Tamers to reduce felt recoil.
I've thought about having them reamed to 9x21 so I can shoot 38 supers in them, but the additional recoil concerns me.
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I don't have Alzheimer's- My wife had me tested.

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I've had a couple of 940s and they're great guns, just too heavy for what they are. That's why I bought the 360J in the first place, to have it turned into a 13oz 9mm snubby because all the others - 940, SP101, 905 - weighed around 22oz, just too heavy for the type of carry I had in mind. The Ruger is lighter at 17oz but they weren't making them at the time.

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Don't kiss smiling dogs!

I I can understand the appeal of sharing ammo across a few platforms, but why carry 9mm in a 340? Why not just carry light .357?

Sent from my LGLS991 using Tapatalk

Because the recoil and muzzle blast from a 13oz, 1 7/8" J frame .357mag are brutal!! The 9mm is a more efficient cartridge than either the .38spl or .357mag so you get substantially improved performance over .38spl +P with similar bullet weights but without the recoil and muzzle blast of the .357mag.

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Don't kiss smiling dogs!

I'd love to see chronograph results. Not sure it would be that much better than .38 + p

Sent from my LGLS991 using Tapatalk

I like it. Good choice on going with Pinnacle. Might be another 10 years before S&W decides they want to go back to making a 9mm J frame.

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Ephesians 6 (Armor of God)

Okay. Here are some chrono numbers that I measured about 8 years ago when I first started experimenting with 9mm snubbies and having my 360J converted. I'd bet that current 9mm ammunition would perform even better considering the effort put into it's development compared to .38spl.

S&W 637 .38spl
WWB 130gr FMJ = 689fps
WWB 125gr JHP +P = 832fps
Fed Hydra-shok 110gr JHP +P = 873fps

Taurus 905 9mm
Magtech 115gr FMJ = 1057fps
Fed 9BPLE 115gr JHP +P+ = 1174fps

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Don't kiss smiling dogs!

Seems i missed the discussion here but it folks like wc145 certainly inspired my project. Thanks for chiming in.

As for the 9mm vs 38sp, I don't have a chrono but I really like the site ballisticsbytheinch.com they post methods and results and don't seem to have a bias. Sure it's only one source but it's quite thourogh and FWIW I use it as a reference. The numbers there certainly suggest 9mm is better out of a short barrel.

Moving on to 9mm vs 357. Reduction in recoil and concussion are the biggest advantages. Those who've shot a ultralight/short 357, you know what I mean. A while back I took several revolvers for a range day. Included were a 44mag 329pd, and this 340. Without a doubt the loudest and most painful to shoot is the j frame. However with the 9mm I can shoot as much as I'd like. I've never put more than a few cylinders of 357 though it at once. And it's not just recoil full power 357 loads are headshakingly loud, as in the range master comes by to see what your shooting loud...

At this point I'm several hundred more rounds of 9mm into the gun, probably ~450-500 total of 9. It is a frequent carry gun now and I'm very happy with it. It's pleasant to shoot and I haven't had issues with ammo. 100% reliable so far. I've gravitated toward aquila 124 for practice, it's nicely crimped which eases my mind about bullet creep. I'm carrying remington 124 sabers, which shoot similarly and have adequate ballistics characteristics per my research.

Another huge advantage for the 9mm is the short snub ejector for provides full length ejection versus 38/357 cases sometimes not fully ejecting with the short rod

Wonder if I can shoot .38/.357 in my 986 no I never tried
would I still need the moons

Your 986 9mm chambers are no doubt cut so that the 9mm round headspaces on the case mouth so they wouldn't be deep enough to take either .38spl or .357mag. In addition, the chambers,like the 9mm case, are tapered and larger in diameter at the base than the .38spl and .357mag so even if you could load and fire them you would have the same case swelling/splitting issue as I do in my converted cylinder.

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Don't kiss smiling dogs!

I agree and have loaded a lot of .38 Special ammo with 9MM bullets. Some 9MM bullets 'mike' at .356 as well as most .38/.357 bullets. I was given several thousand 9MM bullets a couple years ago and had to find a way to use 'em up so many went down a .357 barrel!

Bonkers, your points are well taken, but for the most part they are theoretical vs real world concerns for me. I don't plan on shooting much 357 from the gun. It's kinda of a novelty but I've done it and don't see much reason to. Can I, sure and yes I risk case failure, plus they can be hard to extract d/t expansion. It'll be a fairly rare occasion. I have other 357s and i assure you a range day w/ this gun is more fun w/ 9mm. In large part i did it as an experiment/project. I like the results, but it certainly has down sides. At this point, b/c it's not my only j frame this is pretty much a dedicated 9mm.

The conversion was ~250 including some moon clips, shipping etc. If you assume a 10cent difference b/w 9 and 38spl that's 2.5k rounds till I break even (The numbers are gross estimates b/c I like easy math) Still I will probably shoot that and more from the gun so maybe it make $ sense.

It does offer the ability to carry a back up w/ the same round my primary. I'm not usually a 2 carry gun kinda of guy, so again more theory vs reality. Also this theory often overlooks the moonclips, which certainly complicate round exchange. I do like the way moon clips carry, and 9mm slips into a pocket less noticeably than 38/357.

9mm is easier to find, so that's nice, but I'm very unlikely to stop shooting 38spl entirely. I have to many guns in the caliber that I enjoy! I suppose I can now save my 38 for other guns.

I had and shot a taurus 9mm revolver a bit and I liked it, but it was heavy. Fine for the range but not a gun I wanted to carry. Also taurus is no S&W, another discussion entirely (and some are good guns). The ruger LCR would probably be my choice for an off the rack 9mm, but it's heavy too. A dedicated 9mm cylinder is nice in that it headspaces on the case and your not obligated to use moon clips. Extraction can become a problem though. Should anyone ever make a 9mm ultralight that has a short cylinder I'd jump on it. I even thought about contracting a gunsmith to cut the cylinder and pushing a longer barrel in as you see with some 45's like the 625, but cost is prohibitive as you might imagine. I never got hard #s though.

The new kimber and korth revolvers do look interesting FWIW, not sure if they offer a 9mm clambering but hey more cool guns to consider