Mod 66 9mm Conversion

[K-22]

Would it be possible/practical to convert a Mod 66 to shoot moon clipped 9mm as well as .38 sp/.357 mag?
Best,
Gary

 

[colt_saa]

Gary,
It is a piece of cake.

Purchase a second cylinder for your revision of the Model 66 and send it off to one of the various companies that does rechambering

The cylinder may or may not need to be fitted. The older 66s are a 50/50 shot while the newer CNC manufactured revolvers are drop in about 95% of the time

Personally, Mark at Pinnacle has been doing my cylinder work for many years now

 

[steelslaver]

shouldn't be a problem. the 940 was a J frame 9mm. Just need the cylinder relieved.

 

[Sgt911]

S&W Firearms Revolver Cylinder Machining - TK Custom

 

[Seadragon]

Converting a 66 to shoot moon clipped 9mm is no problem. But you should be aware that the 9mm cartridge has a wider base diameter than the .38 (.391 vs. .379 inch) which may result in the .38 brass being hard to extract since it will swell when fired in the enlarged chamber.

 

[colt_saa]

Converting a 66 to shoot moon clipped 9mm is no problem. But you should be aware that the 9mm cartridge has a wider base diameter than the .38 (.391 vs. .379 inch) which may result in the .38 brass being hard to extract since it will swell when fired in the enlarged chamber.

This is not a problem when you have two cylinders

You should not be shooting 357 Magnum in your 9MM cylinder anyway

While it can be done without the risk of a catastrophic failure of the firearm. Split casings are a common issue with certain brands of ammunition.

Not to mention that hand-loaders do not like the way the brass comes out. It is much harder to resize. Case life is also adversely affected

 

[Murdock]

Easy peasy. The second cylinder I got for my M60 snapped right in without any hand fitting. Sent it to TK Custom. Quick turnaround. Superb work. When you are done your M66 should handle .380 and .38 Super as well as 9x19. Buying a second cylinder means you have not modified the original gun, so no harm to its value. The modded cylinder still handles .357 and .38 Spl, so you don't need to switch them back and forth at the range.

 

[stansdds]

Converting a spare cylinder is, in my opinion, the best way to do this.

 

[DonD]

No intent to be critical here, just wonder if shooting 9mm which is .355 in a revolver with a bore of .357 results in blowby and significantly increased bore wear? Don

 

[stansdds]

No intent to be critical here, just wonder if shooting 9mm which is .355 in a revolver with a bore of .357 results in blowby and significantly increased bore wear? Don

Good question and my first answer would be "yes", but I think the bigger issue will be bullet stability or lack thereof due to poor engagement with the grooves. I'm not sure what bore and groove diameters S&W used in their dedicated 9mm revolvers. Perhaps those who own such revolvers can shed some light on this potential matter?

 

[Protocall_Design]

No intent to be critical here, just wonder if shooting 9mm which is .355 in a revolver with a bore of .357 results in blowby and significantly increased bore wear? Don

It's not a problem with either lead or jacketed ammo. I have shot a lot of .355 bullets in .357 barrels and a lot of .357 bullets in .355 barrels. If the gun is mechanically correct, especially the forcing cone and muzzle crown, and no choke in the barrel to frame area, you can normally get good performance with any combination. As with any gun, some loads will be more accurate than others, but not always the same loads for different guns of the same model number.

 

[Lou_the_welder]

I'm wondering if the OP meant on the newer models. The 66-8(?), where the cylinder is captured in the yoke and not easily removed.
Well, my response might be more for both I suppose. Old model 66's and newer.

I shot 9mms out of my model 66 without any modifications to the gun. Didnt have to send the cylinder out. Didnt have to wait for it.
"What?! How did he do this?! "

I loaded 9mm bullets on 38 short colt cases. No great feat, considering I make bullets. Have plenty of 9mms laying around.

The 9mm doesn't bounce around a 357 barrel. The bullets do engage the rifling and twist. That's all you gotta know.
I've fit 357 barrel pilots in 9mm barreled semiauto's. Same thing.
Maybe an industry secret?[emoji848]
Anywho.
Great accuracy. Had lotsa fun. If it wasn't for the fact that I'm a brute and K frames heat quicker than L's, I'd still be shooting it.
Like I said ,had lotsa fun.
I still shoot 9mms out of my 327/627's.