22 conversion 18 to 648

[riversalmon]

Is the smith 648 mag cylinder the same dimension externally as a model 18 ? Is the cylinder longer or shorter on the 648? Wanting to put a mag cylinder in my 18.
For conversion with out crane assembly.

 

[s&wchad]

The short answer is yes, they're the same length (1.62"). There were changes to the gas ring over the years, so they may not be compatible.

Personally, I wouldn't recommend this conversion and consider it a bad idea.
.22 MRF barrels have a larger bore diameter than .22 L.R.'s.
In the past, Smith & Wesson would fit a L.R. cylinder to a customers M.R.F. gun, but they wouldn't fit a M.R.F. cylinder to customers L.R..

 

[MygunisaS&Wrevolver]

I don't know for sure if they are the same dimensions. If they were, it would require fitting the yoke/crane and cylinder and involve the barrel cylinder gap, headspace and ratchet fit. This is a complex job that is best left to a S&W gunsmith and it could mess up returning the original cylinders back to the original guns.

 

[MygunisaS&Wrevolver]

s&wchad is right on the bore size issue, I think the model 18 barrel is .002 smaller than the 648.

 

[colt_saa]

Why not just get a second Model 18 cylinder and rechamber it to 22 Magnum?

That is all I did for my model 34

 

[S.B.]

The short answer is yes, they're the same length (1.62"). There were changes to the gas ring over the years, so they may not be compatible.

Personally, I wouldn't recommend this conversion and consider it a bad idea.
.22 MRF barrels have a larger bore diameter than .22 L.R.'s.
In the past, Smith & Wesson would fit a L.R. cylinder to a customers M.R.F. gun, but they wouldn't fit a M.R.F. cylinder to customers L.R..

I got in touch with S&W about fitting a new cylinder to my model 17(to send to be reamed to .32) for a project gun I'm considering(have since found a K .22LR cylinder on Fleebay) and they said YES they could fit one to my particular - numbered gun. Keep in mind the dash number is their determining thing, here.
Steve

 

[steelslaver]

The .002 in bore diameter isn't a problem. .224 mag bullet instantly becomes a .222 bullet when it goes through the forcing cone. A k22 would even notice it.

PO Ackely regularly did things like fire 8mm bullets (.321) in .308 barrels using guns that that where set up to properly chamber the 8mm bullet.
P.O. Ackley 1966 "Handbook for Shooters
and Reloaders Vol 2" chapter 7
"additional pressure tests":
"..30 cal barrel pressure barrel was fitted to the test gun, but the
neck and throat was enlarged to accept the 8mm bullet, with the bore remaining the standard 30 caliber. A Remington factory 30-06 cartridge with the 150 gr bullet had been tested and previously gave 57,300 psi, for a velocity of 3030 fps. The the bullets were pulled from two more Remington 150 grain cartridges and were replaced with 8mm 150 grain
bullets. To everyone's surprise, although the velocity was rather erratic, these loads averaged 2901
fps, with a pressure of 40,700 psi."



Guys regularly shot .454 bullets through .452 barrels on big throated cylinders on 45 colts like the early 25-5 guns.

 

[mike_engr]

I have a barely used 648 I'm gonna sell soon, but til then I could take some measurements for you. PM me or post here exactly what you want, such as the overall length of the cylinder from front to back (not including the ejector/clocking notches, etc.. ??)

I have a digital calibre that's accurate to a couple thousandths I would think.....

 

[bgrafsr]

The .002 in bore diameter isn't a problem. .224 mag bullet instantly becomes a .222 bullet when it goes through the forcing cone. A k22 would even notice it.

PO Ackely regularly did things like fire 8mm bullets (.321) in .308 barrels using guns that that where set up to properly chamber the 8mm bullet.
P.O. Ackley 1966 "Handbook for Shooters
and Reloaders Vol 2" chapter 7
"additional pressure tests":
"..30 cal barrel pressure barrel was fitted to the test gun, but the
neck and throat was enlarged to accept the 8mm bullet, with the bore remaining the standard 30 caliber. A Remington factory 30-06 cartridge with the 150 gr bullet had been tested and previously gave 57,300 psi, for a velocity of 3030 fps. The the bullets were pulled from two more Remington 150 grain cartridges and were replaced with 8mm 150 grain
bullets. To everyone's surprise, although the velocity was rather erratic, these loads averaged 2901
fps, with a pressure of 40,700 psi."



Guys regularly shot .454 bullets through .452 barrels on big throated cylinders on 45 colts like the early 25-5 guns.

I have a replica Sharps 1894 in .40-65. Barrel is stamped either .408" or .410" bore. Leading with standard bullets was atrocious after just a few rounds. Found out the chamber was overly big. I had a couple of custom bullet moulds made that average .417" for the bullet diameter.
Now I get hardly any leading, even after shooting 20 or 25 rounds at steel silhouettes or paper targets. No difference in recoil, that I can tell, with .408" or the .417" bullets.

 

[SuperMan]

Have to agree with steelslaver... I have a number of Smith .22s that have had Magnum cylinders fitted to them.

63 with a 651 cylinder
18 with a 48 cylinder
17 with a 48 cylinder
and my favorite...a 35 with a 51 cylinder.

All of them took very little fitting by a smith I use who was factory trained.

Bob

ps...I think that Ruger and S&W are the only two that use a .224 bore with convertible guns. Everyone else {Freedom Arms, USFA} seems to start off with a .22 LR bore and add a Magnum cylinder that results in much better accuracy for both rounds. A lot of people complain about the accuracy of Smith 48s when used with the extra LR cylinder compared to a 17. Yet a .22 Jet Model 53 was bored .2225 and had great accuracy with their .22 LR cylinder...

 

[mike_engr]

Hey, thanks for the PM.
Below you will find the dimensions you requested.
Measured today my nearly new no-dash 648 I'll be putting up for sale (again) soon.
Link to pictures, for reference purposes:
FS WTS Rare S&W 648 22Mag 6" SST No Lock No Dash in NC

I measured this with my digital Mitutoyo CD-8" CS. I'm reporting a few measurements as I turn the open cylinder a few times...
Hopefully these dimensions will help you and others!

cylinder diameter: 1.452" 1.453" 1.453"

cylinder length to face of cylinder: 1.622" 1.623" 1.623"

cylinder length from the back to the front of the
cylinder gas ring that the ejector rod runs through: 1.820" 1.819" 1.820"
(NOTE: this one toughest to understand/measure, but I mic'd Length from back avoiding the ejector star, to front including the thickness of a non-spinning small Lip that is part of the Crane. Sorry, I'm not willing to disassemble my like-new ~27 year old revolver especially cause I'm gonna sell it soon to fund some other projects...)

I hope these dimensions help!

PS: It's kind of ironic that you want to convert your LR to 22Mag. When I picked this 648 up in early '90's I thought it WOULD shoot 22LR. Disappointed I then thought about investigating conversions to 22LR! Bought a 22LR Ruger target instead and put the 648 Magnum away and its now become rare and a collectible! (Value?? PM me!)