I had a spare top end for my 3913 so I converted it to .357 Sig. Mag capacity dropped to 7 rounds. It launched the factory Corbon 115gr ammo out at 1482fps. My 124gr XTP hand loads ran 1401fps. I fired about 50 rounds. No malfunctions of any kind......a pretty simple conversion really.

Tony Rumore
Tromix

What exactly did you do to convert?

I just rechambered the barrel, mod'd the magazine and opened up the breach face. I have a 20 pound single spring in it, but will probably make a smaller diameter guide rod and run a twin spring setup. No changes to the extractor or ejector. It only took about 2 hours to do it.

Tony

SAAMI chamber pressure for both is 35,000 so it should be not more abusive on the pistol. I've been thinking about doing such a conversion for a few months now. Been also watching out for a Beretta cougar 8357.

Curious, why did you need to modify the mag?

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USS ZELLARS
DD-777

The magazine is only wide enough to hold 9mm rounds, not 40SW/357 Sig.

Tony

Very nice...a singular piece. I really like that cartridge...

First let me say Welcome to the Forum

Nicely done conversion.

If I did not already have a 4014 converted to 10MM Auto I would probably pursue one of those 3913 conversions.

You could have gone to 356TSW with less work and no loss of rounds, however the 357SIG ammunition is much, MUCH easier to get a hold of than 356TSW

I wonder if mags for a 4040PD would work? Same frame size...

I have to admit I'm pretty interested by this conversion. I have thought about converting some all-steel S&W third gen's to .357 Sig. Another suggestion I have is to see whether you can get the recoil spring assembly for a 4040PD. The 4040PD has a dual spring assembly and it should fit a 3913 slide and provide additional resistance. (Caveat - I sold my 3913 many years ago--yes, I regret that--so I can't try swapping out the recoil spring from my 4040PD.) How were you able to get "357 SIG" engraved on the slide?

Seems that the enlagement of the mouth of the chamber to .40 specs (approx .040" larger) would make the chamber wall very close at the bottom, where the chamber, hood, and the supported ramp meet. Any integrity/pressure concerns here?

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Ret. LE, FA Instr, S&W Armorer

I have an engraving machine.

Tony

Here's a pic of the 9mm and 357 Sig barrels side by side.

Tony

Hi, Tony!
Welcome to the forum!
Cool conversion!
Please tell me how you "opened up" the breech face.
BTW, isn't the SAAMI spec on 357 SIG 40,000 psi?

John

me want it

Me too...!

Yeah, the Sig is 40k. Some guys would not be comfortable shooting this type of conversion and that's certainly understandable. However, I personally don't have a problem with it.....so I'll be shooting it, but not selling it.

Just for testing purposes, I took the .357 Sig top end, with it's larger breach face and installed the 9mm barrel in it, leaving the 20 pound recoil spring, and used the .357 Sig magazine. It functioned perfectly in 9mm.

So, with a .357 Sig top end, it only takes a barrel swap to go back to 9mm.

Tony Rumore
Tromix

Welcome to the forum!

Sure is a neat conversion.

In reference to post #6,I tried a variety of 9mm S&W 3rd gen magazines with a 40S&W cartridge and the 40S&W cartridge fit well/easily into the 9mm magazines.
Seems to me that along with the small single 9mm S&W pistols,69XX series and 59XX series could also be converted to 357Sig.

6904 or 6906 conversion like this would seem to be a natural next step


Sent from my iPad using Tapatalk

Pulled some barrels and did some measurements

The 4053 barrel isn't really applicable to the scenario as it's built on the 45 frame. I don't have a standard 40S&W barrel.
If TONY could supply some dimensions for his pic in post#13,we could see what the wall thickness ended up as.

Took TONY's pic in post#13 and put it in photoshop along with my pic and did some dimensioning. I come up with a .090" wall for his 3913 barrel reamed to 357Sig.

Attached Images

DSC_4796 CC&A&C wTs A S.jpg (234.5 KB, 135 views)

Ooh, a 5906 or 6906 in .357 Sig would be sweet.

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What would Jim Cirillo do?

Cool pistol!

Anyone know the difference in ballistics between the .357 SIG and the .356 TSW?

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Because of the metric system?

Years ago, I shipped my M39-2 to Barstow for a fitted barrel in 9X21. Bought a big box of Starline brass. Switch barrel conversion.

Note: Barstow no longer offers S&W barrels.

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NRA LIFE
Reserve Officer 9yrs

Tony, Very interesting project with that 3913. You should make some barrels in your shop for these S&W 3rd gen guns. BadManOne here on the forum had started to do a barrel project but his progress came to a halt due to several reasons...maybe he can get back on this some day! I pray he does because I have 4 barrels in that order should he get to finish up someday.

Yep, Bar-Sto did a few barrels back in the day, I have the 40S&W Match Grade conversion for my 1006. Then later picked up a 9x25 Match Grade conversion from Mike McNett of Double Tap and fitted that for my 1006.

Good luck Tony!

My interest in this is because I reload 9mm with 88/90gr 380acp bullets and achieve 1500fps. A 357Sig loaded with those 88/90gr 380acp bullets ,because of larger powder capacity and using the right powder,should be able to easily surpass the 1500fps threshold.

Virtually identical with 124/125 grain projectiles.

I load the 90 grain JHPs over a nice charge of Power Pistol in the 357SIG and break 1700 FPS without pushing the pressure limits of the cartridge.

^^^ good to hear !

Referring back to my post#21 where I indicated a 9mm barrel reamed out to accept a 357Sig would bring about a .090" wall thickness.
I measured some revolvers for chamber - cylinder thickness and thickness between chambers.
1st dimension is chamber to cylinder OD thickness,2nd dimension is thickness between chambers.
N frames
M28 .110" .155"
M610-2 .092" .110"
M57 .088" .103"
M629-3 .078" .080"
M629-6 .073" .080"
L frames
M586 .084" .111"
M686-6+ .078" .050"
M69 .050" .123"
K frames
M65-2 .075" .067"
M19 .073" .066"
J frame
M60-15 .044" .095"

There are MANY dimensions in the revolvers that have less than the .090" wall of a converted 9mm to 357Sig barrel.
Of the 22 dimensions,14 are less than .090".

Tony,

Very interesting conversion. The 3913 and 3914 are my favorite S&W models. I was wondering what the recoil feels like compared to 9mm?

I have a pair of 4046s that I've thought about making switch barrel conversions for, if I could only find a 9mm barrel that fit a 40 slide.
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I don't have Alzheimer's- My wife had me tested.

This is fantastic, and the 3913 is one of the prettiest looking pistols out there.

Are there any updates on this? Or do we know anyone who makes barrels?

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July 4, 1776 not Jan 30, 1909

Damn , but you really put an idea in my head . I have a CS40 that was converted to 10mm , Then I bought a m4013 I was going to convert , and now you're messing with my head . I have another m3913 coming , so what do I do ? Contact BMCM and see if this is something he can do ? The only thing is , am I disgracing the S&W gods by going to .357sig ?

There is no disgracing of the S&W gods

Smith and Wesson has built many 10s of thousands of firearms chambered for the 357SIG cartridge over the decades

Back in 1993 a single tool room sample of a Shorty 357 was produced. I am guessing that they wanted it for cartridge testing, though it was obviously used for market testing as well

The first production run was the 357 SIGMA which came along later in the 1990s
While it is not known how many SW357V pistols were assembled, I do know they had 1500 barrels, so the total pistol production had to be less


With the introduction of the M&P line of autoloaders in the early 2000s the 357SIG cartridge was made available in both full size and compact versions
There are no production figures on these, but LOTS of them are out there

After all this time.....

I'm still waiting to hear how the 9mm breech face and extractor of the 3913 was modified to fit the 40s&w size base of the 357sig cartridge.

Crickets....

John

P.S. I've done a couple of 357sig conversions on S&W 3rd gen 40s&w pistols.

Old thread revival ! Being a big fan of the 357 SIG cartridge, this thread is fascinating. Make me wonder if my model 39 (I think it's a -2) can be converted to 357 SIG. I believe my gunsmith friend has a 357 SIG chamber reamer. I am curious how the OP modified the 9mm Mag to take the 40/357 Sig cartridges.

Bringing up an old one.
After the 4046TSW Sig conversion, this has me thinking about that spare 3913 wide hood slide sitting in my parts box.
Either on a 908 frame or a 3913 frame.
Already have some 4040 mags.
Parts in hand, what to do?

Do the 4040 mags fit in the 908 and 3913 frame?

If so, that would make a very nicely. Proportioned single stack in 357 SIG.

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"Acta non verba"

Yes they do.
I swapped in 3913 followers and they feed and function in my 908.
Still have the 4040 followers.