Changing cylinder in S&W J frame from 38spl to 9 mm

Number 6

NES Member
Joined
Nov 2, 2008
Messages
334
Likes
30
Location
Metro West MA
Feedback: 12 / 0 / 0
I'm thinking of taking advantage of the current $50 rebate on S&W J frames but really don't want to get into buying a new caliber (38spl). In doing some reading it seems S&W did at one time make a 9mm J frame (940).

Seems people have swapped out the 38 spl cylinder in their J frame for a 940 cylinder sourced from either S&W or Brownells. Others have sent their 38 special cylinder to a gunsmith for them to hone out and make cuts for the necessary moon clips.

I really like the idea of staying with 9mm and having a J frame for would be great.
Has anyone done this or happen to know if this is ok to do?
Apparently the difference between the 9mm and 38 special is .001, so the barrel is not an issue.

Number 6
 
Last edited:
I haven't had done this but a few comments:

I'm guessing the $50 rebate is going to pale in comparison to how much a new cylinder and the fitting will cost

I know of some people who have used 9mm projectiles in .38 cases (in .38/.357 guns) and their performance was very sensitive to the (taper) crimp that they used on the bullets. I looked and couldn't tell if the barrel in the 940 was different than the 640 but that 0.001" may affect things more that you think.

Do you reload or do you buy ammo? For defensive ammo the cost isn't that different, but for target ammo .38 is ~1.4-1.5x more expensive. If you reload the cost of my .38 and 9mm loads are very close (if you are using "free" range brass). I'm just not sure it's worth the cost & hassle to have it done. I know the 940's are rare and have a premium price. I think Ruger made the SP-101 in 9mm. I'm not sure how rare they are.
 
I have an SP-101 that was rechambered to 9mm from .357mag and recessed for moonclips. No change needed to be made to the barrel, since the throat handles the minimal difference just fine. It is stupid accurate with 9mm. Uses the same full moonclips as the 940, which can be had from several sources. There are a couple of gunsmiths that specialize it this conversion. Most notably Pinnacle Guns and TK Custom get good reviews.

Well worth doing in terms of function. Price? It is expensive to do ($250). Lucky me, mine was bought used. If you can find a 940 or SP-101 already set up the way you want, I'd go for it.

Also: I'd recommend doing this with a revolver that started life as a .357mag, not .38 Special. Look at the pressures for 9mm - let alone 9mm+P and compare with .38 special and you'll see what I mean.
 
Last edited:
I don't think the conversion is worth the money. There is nothing that the 9mm does in this pistol that the 38 can't do, except use moon clips. The difference between a 9mm (.355) and a 38 (.357) is huge. You may get decent performance with jacketed ammo, but lead bullets will probably key hole.
 
I don't think the conversion is worth the money. There is nothing that the 9mm does in this pistol that the 38 can't do, except use moon clips. The difference between a 9mm (.355) and a 38 (.357) is huge. You may get decent performance with jacketed ammo, but lead bullets will probably key hole.
You are entirely mistaken.

From a snub, there is almost a 275fps difference between 9+P and .38 Special+P.

But, because .357mag is not really a short barrel load, it'll run only about 100fps faster than the 9+P with a huge fireball (and that's with full-on .357mag; Speer's Short Barrel .357mag load will be going SLOWER than the 9+P).
 
Also: I'd recommend doing this with a revolver that started life as a .357mag, not .38 Special. Look at the pressures for 9mm - let alone 9mm+P and compare with .38 special and you'll see what I mean.
That's too bad. I have an SP-101 in .38 Spcl gathering dust in the back of the safe. A 9mm SP101 might be more interesting to me.
 
That's too bad. I have an SP-101 in .38 Spcl gathering dust in the back of the safe. A 9mm SP101 might be more interesting to me.

Yeah, though SP-101s seem really over-built to me. I would discuss with a gunsmith who does these conversions whether they think it's safe to rechamber it in 9mm or whether you can swap the cyls for 9mm on that model. I know I've seen some .38 conversions out there.
 
Thanks for the gunsmith tip of Pinnacle, Knob Creek. Any experience with them or know anything about them?

Wonder if any MA shops would do this work.

It's not so much about the higher price of 38 special, but I'd rather not branch into yet another caliber. I have several 9mm auto pistols and it would just be very convenient to use the same ammo in a J frame.

During the Great Ammo Shortage of 2009 , it was a rare thing to see a box of 38 special.
 
Last edited:
This thread reminds me of the time I saw a 940 posted on the NES Classifieds once.

I think it lasted not even 5 minutes. [laugh] I would wager a guess it was one of the shortest
classified ads ever on NES.

-Mike
 
You are entirely mistaken.

From a snub, there is almost a 275fps difference between 9+P and .38 Special+P.

But, because .357mag is not really a short barrel load, it'll run only about 100fps faster than the 9+P with a huge fireball (and that's with full-on .357mag; Speer's Short Barrel .357mag load will be going SLOWER than the 9+P).

The problems you allude to are due to the bullet weight and the burning rate of the powder. With the proper loads the 38 will perform just as well as the 9mm. You also failed to address the accuracy problems due to the difference in bullet diameters.
 
The problems you allude to are due to the bullet weight and the burning rate of the powder. With the proper loads the 38 will perform just as well as the 9mm. You also failed to address the accuracy problems due to the difference in bullet diameters.

You're right, he didn't address it...in that post. But if you look a couple of posts above, he clearly says:
I have an SP-101 that was rechambered to 9mm from .357mag and recessed for moonclips. No change needed to be made to the barrel, since the throat handles the minimal difference just fine. It is stupid accurate with 9mm. Uses the same full moonclips as the 940, which can be had from several sources. There are a couple of gunsmiths that specialize it this conversion. Most notably Pinnacle Guns and TK Custom get good reviews.

And notice that's "I have..." vs. "Gosh, I think..."
 
I converted a S&W 60 to 9MM. It was an easy conversion done by buying a 9MM barrel and cylinder from S&W. I got the last set available. No more OEM parts available. I know this because I sold mine to a guy I know and was going to build another. Should have checked on parts before i sold.

There is a huge difference in performance between 38spl and 9MM using factory carry ammo. 9MM out performs 38spl from a 2" barrel in all tests for expansion in gell and in consistency.

What you can custom load is a moot point since most carry factory ammo rather than hand loads.

Pinnacle is a good company to deal with from what I have been told but I do not see the conversion as worth the expense on a J frame now that factory parts are no longer available. Not sure but I don't think Tom at TK does this any more.

Edit to add: I think total cost of conversion parts and labor was $300
 
I converted a S&W 60 to 9MM. It was an easy conversion done by buying a 9MM barrel and cylinder from S&W. I got the last set available. No more OEM parts available. I know this because I sold mine to a guy I know and was going to build another. Should have checked on parts before i sold.

Can you comment on the performance (accuracy, velocity) of not swapping the barrel and using the .38sp one?
 
Can you comment on the performance (accuracy, velocity) of not swapping the barrel and using the .38sp one?

It would totally depend on the barrel and how tight it was. You could load 9MM brass with .357 bullets and have little to no problem but as a carry gun, I would want to stick with proper barrel and cylinder.
 
You're right, he didn't address it...in that post. But if you look a couple of posts above, he clearly says:


And notice that's "I have..." vs. "Gosh, I think..."

We are discussing the conversion of a S&W revolver from 38 to 9mm. I didn't think that the results of a similar conversion using a Ruger was relevant.
 
We are discussing the conversion of a S&W revolver from 38 to 9mm. I didn't think that the results of a similar conversion using a Ruger was relevant.

Fascinating. You said:
The difference between a 9mm (.355) and a 38 (.357) is huge. You may get decent performance with jacketed ammo, but lead bullets will probably key hole.

...and now it's about Ruger vs S&W? Is the bore on a 9mm and .38 Ruger somehow different than a S&W? Gosh, I learn something new here everyday.
 
Fascinating. You said:


...and now it's about Ruger vs S&W? Is the bore on a 9mm and .38 Ruger somehow different than a S&W? Gosh, I learn something new here everyday.

Barrel dimensions can differ quite a bit from one manufacturer to another.
 
That's awesome, I had no idea it was so straightforward to re-chamber a revolver. Sending my S&W J-Frame off to become a 9mm is now on the to-do list. That's not that expensive given the cost of a new revolver.
 
Buf Bore's own 9mm loads outperform its .38 Special +P by 175-250fps.

I am talking about their #20A 158 grain LSWCHP +P load.

tem 20A: 158gr., very soft cast, semi wad cutter, (Keith) hollow cavity, with a gas check. This bullet will mushroom violently on impact and will penetrate roughly 14 inches in human flesh. Again, this bullet is gas checked and will not lead your barrel.

S&W mod. 60, 2 inch- 1040 fps (379 ft. lbs.)
S&W mod. 66, 2.5 inch- 1059 fps (393 ft. lbs.)
Ruger SP101, 3 inch- 1143 fps (458 ft. lbs.)
S&W Mt. Gun, 4 inch- 1162 fps (474 ft. lbs.)



Their only 9 mm load even close to it is their +P+ 147 grain #24C/20


Item 24C/20 (+p+) 147gr. Jacketed Hollow Point

Browning Hi Power MK111, 4.6 inch barrel----------1179 fps
Beretta 92F, 4.9 inch barrel------------------------------1131 fps
Glock 19, 4.0 inch barrel---------------------------------1165 fps
 
That's awesome, I had no idea it was so straightforward to re-chamber a revolver. Sending my S&W J-Frame off to become a 9mm is now on the to-do list. That's not that expensive given the cost of a new revolver.

The cost I quoted were my discount on parts and the gunsmith that actually fitted them. Sending for a conversion will probably run a lot more. Also, make sure it is not a light framed revo as I don't think anyone will do them
 
I am talking about their #20A 158 grain LSWCHP +P load.
Wow - That is an impressive load even comparing the 3" revolver barrel to the 4" semi barrel (because of how they're measured). Thing is, this is snubs we're talking about, and, as those numbers reflect, in something like a Model 60, even Buf bore's .38 Spec. is not such a hot performer (1040fps) for the same reason .357 mag isn't. You just can't get enough burn fast enough without exceeding the cartridge specs for pressure. The longer the barrel, the more you can milk it, and that Buf Bore round does that amazingly.
 
Wow - That is an impressive load even comparing the 3" revolver barrel to the 4" semi barrel (because of how they're measured). Thing is, this is snubs we're talking about, and, as those numbers reflect, in something like a Model 60, even Buf bore's .38 Spec. is not such a hot performer (1040fps) for the same reason .357 mag isn't. You just can't get enough burn fast enough without exceeding the cartridge specs for pressure. The longer the barrel, the more you can milk it, and that Buf Bore round does that amazingly.
Dude........

1000 fps out of a 1 7/8" barrel with a 158 grain bullet is f-ing hardcore.

I've chroned that load out of both my 637 snub and my 4" Model 64 and my numbers match BB's within 10 - 15 fps.

They are not exaggerating. I got an chronographed 1160 fps 10 feet from the muzzle out of a 4" Model 64.
 
That's awesome, I had no idea it was so straightforward to re-chamber a revolver. Sending my S&W J-Frame off to become a 9mm is now on the to-do list. That's not that expensive given the cost of a new revolver.

It isn't cheap- but the alternative is a USED factory S&W 940 - now that's Expensive!
 
Dude........

1000 fps out of a 1 7/8" barrel with a 158 grain bullet is f-ing hardcore.

I've chroned that load out of both my 637 snub and my 4" Model 64 and my numbers match BB's within 10 - 15 fps.

They are not exaggerating. I got an chronographed 1160 fps 10 feet from the muzzle out of a 4" Model 64.
Ok, then I agree it's pulling out some oomph up there with and beating most 9 +P+ power. But that still means 1040fps/158gr out of a snub. I guess I don't see why, with the pressures obviously jacked to the max to do that, you wouldn't just shoot .357 mags unless you only have a .38+P cylinder?
 
Back
Top Bottom