Convert K-22 cylinder to .22 WMR?

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jonathan.byrne

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I know it has been debated before but I want to bring it up again. I have a 1948 K-22 that I would love even more if I could shoot the .22 WMR out of it. It seems like 70% of forum members think it is a bad idea but I am not convinced they are taking into account the awesomeness of the K-22.

Yes, I know that the .22 WMR bullet is .224" diameter and the .22 LR bullet is .223" diameter. Yes, I know that a larger diameter bullet will increase the pressure in the barrel. However, the K-22 has always struck me as very over-engineered. For comparison, consider the following:

1948 K-22
Barrel outer diameter: .580"
Barrel maximum inner diameter: .224"
Cylinder wall minimum thickness: .150"
Cylinder inner diameter: .220"
.22 LR maximum pressure: 24000 PSI
.22 WMF maximum pressure: 24000 PSI
Cylinder hoop stress at maximum pressure: 34464
Barrel hoop stress at maximum pressure: 32414

Model 10
Barrel outer diameter: .543"
Barrel maximum inner diameter: .359"
Cylinder wall minimum thickness: .088"
Cylinder inner diameter: .358"
.38 Special maximum pressure: 17000 PSI
Cylinder hoop stress at maximum pressure: 44756
Barrel hoop stress at maximum pressure: 43402

Notes:
  • I took the measurements with a cheap micrometer so they might be a little off.
  • Hoop stress was calculated using Lame's formula: Pressure * (OuterRadius ^ 2 + InnerRadius ^ 2) / (OuterRadius ^ 2 - InnerRadius ^ 2)
​
​

The chamber pressure of a K-22 modified for the .22 WMF should be exactly the same as the Model 48 which was designed to chamber the .22 WMF. The only difference between the K-22 and Model 48 would be how fast the pressure decreases in the barrel. Based on the numbers above and assuming the K-22 was using the same steel alloy as the Model 10, I think the K-22 barrel should be able to easily handle the additional pressure.

Any thoughts on this?
 
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glowe said:
Depending on the condition of your 1948, whether it has a single line or 4 line stamping on the frame, you can take a potentially $1000 gun and make a $400 gun out of it and shoot 22 WMF all day. You could also sell that one to a collector and go out and buy a new 22WMF revolver.

My sentiments as well. Just because you can, doesn't mean you should.
Click to expand...
 
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Seems like M-48s come up for sale regularly, maybe even one on this forum right now?
 
glowe said:
Depending on the condition of your 1948, whether it has a single line or 4 line stamping on the frame, you can take a potentially $1000 gun and make a $400 gun out of it and shoot 22 WMF all day. You could also sell that one to a collector and go out and buy a new 22WMF revolver.
Click to expand...

I should have added that I was going to find a replacement cylinder and have a gunsmith bore and fit that while leaving the original intact. If the gunsmith couldn't fit the new cylinder without modifying the gun, I would leave it intact as a .22 LR.

It's a one liner but the bluing is a little worn in spots and there are a few small dings on the barrel. It was my grandfather's so there is also some sentimental attachment that would keep me from selling it.
 
Welcome to the Forum

Your project is possible

22 Rimfire pressure surrounded by that much steel. . . there is no need to worry about a catastrophic failure of your Smith and Wesson revolver.

It is your firearm, do what pleases you.

I have a Model 34 setup up with dual cylinders so I can swap

34%20convertible%20small.jpg

If you create a second cylinder for the 22WMR, I can not see how the value of your revolver can possibly drop 60% since you can return it to it's factory shipped configuration any time that you please.
 
Use the 'Search' function and find the myriad of threads and post prior on the subject of fitting a second cylinder that has been reamed to 22 MRF. It is a straightforward job. You can usually find a suitable cylinder on ebay.

The difference in OEM barrel diameter is insignificant. IMHO, the 22 mag thru a 22 LR barrel is usually more accurate than thru the OEM barrels for 22 mag.

By all means get a second cylinder and do not touch the original one. The second can be fitted without touching any part of your original handgun frame or internals. It is an easy task to switch cylinders when desired. It won't make any difference if the second cylinder is blued or stainless. It is required that the second cylinder has the exact same design of extractor star as your original. When purchasing the to be acquired second cylinder make the vendor measure what is being offered and do not purchase if it is more than 0.004 to 0.006" longer than yours.

Please keep the forum informed of your progress. ....
 
You guy's that worry about pressure caused by a .001 increase in bullet diameter need to get the 2 volume set of P.O. Ackleys books and read the chapter on pressure. In this chapter He uses a pressure gun and bullets larger than the bore. He ststes that as soon as the bullet enters the bore completely it is resized to the bore diameter and only a minimum in pressure increase is present for that time. It's not as if the bullet stays at .224 all the way. I have been shooting .223 and .224 bullets through My Model 53 for almost 30 years with no problems whatsoever.
 
Yes, slightly larger than the "correct" diameter bullets will have no noticeable effect upon pressure. They just squeeze down and keep on going. I have told the story previously about the 8mm German Model 88 commission rifle. These were originally made for .318" RN bullets (8x57J). During the WWI period, many were altered (by opening up the chamber throat diameter slightly) allowing use of the later 8x57JS (for "Spitzer") military cartridge which used a .323" diameter bullet. The M88 was not noted as having a particularly strong action and the barrel (inside a tubular jacket) is fairly skinny. Yet the conversion apparently worked fine. I had one of those converted M88s once, and fired many rounds of WWII-era German 8mm military ammo through it with no issues.

Has anyone ever seen any pressure-damaged revolver barrel, other than one caused as the result of a bore obstruction (such as a stuck bullet)? I never have. It's virtually impossible for that to happen because the barrel-cylinder gap is essentially a built-in pressure relief valve.
 
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I agree. The only concern here is finding a spare K frame 22 cylinder, reaming it and fitting it. The pressure of doing this is .00000000nothing.

Oversized bullets only blow up guns when coupled with other factors. Gross head space, gross overload, a poor cartridge to chamber fit in some manner that lets pressure out in the wrong directions.

Something like a .318 bullet loaded in a 30-06 might be a problem, but, not because of bore diameter. But, because of the chambers neck and throat diameter clamping down hard on the neck and bullet base because of the increased diameter in this area and making it difficult for the bullet to start moving.

As stated read about some of PO Ackely's experiments. A .224 bullet in a .222 bore is basically a non event.
 
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In "Hatcher's Notebook" Hatcher discussed firing a .45 ACP cartridge in a M1903 rifle without damage - Just a very long .30 bullet came out of the muzzle.

It is important to have a chamber throat slightly larger than the cartridge case neck. There must be some room available to allow case neck expansion during firing to allow the bullet to be released from the case easily or chamber pressure can build very rapidly which could be catastrophic. That is why the Germans modified the M88 rifle chamber as they did.

"Something like a .318 bullet loaded in a 30-06 might be a problem, but, not because of bore diameter. But, because of the chambers neck and throat diameter clamping down hard on the neck and bullet base because of the increased diameter in this area and making it difficult for the bullet to start moving."

And in fact that happened. Most may be familiar with stories about the "danger" of firing the early "low number" M1903 Springfield rifles because their brittle action can blow up in the shooter's face. Hatcher also discusses that, indicating that a disproportionate number of such blowup events resulted from some soldier firing (or attempting to fire) an 8mm Mauser cartridge in a M1903 rifle. Assuming one can even close the bolt, the 8mm case neck will be swaged tightly into the smaller diameter .30-'06 chamber throat and the bullet will not move when the trigger is pulled. Followed by a Ka-Boom and fragments of action metal flying in all directions.
 
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I don't know what you boys are smokin' or drinkin', but I sure don't want any of it. Have you priced 22 mag ammo recently? So you're suggesting spending even more to convert a fine firearm to shoot a significantly more expensive round? OK, I agree its a free country. Freedom includes the right to be stupid.
 
First I want some of that stuff your a sniffe'n.

I was looking at a s&w m48 4" barrel in 22wmr to move up the misses from the Taurus m94 in 22lr/6" barre.
 
Anyone is free to make such a conversion assuming they have the moolah to finance it. If it wasn't a big deal to find an existing .22 WMR cylinder that was pretty much a drop-in replacement, that makes more sense for anyone wanting a .22 WMR revolver. That would not include me.
 
Talking about tthe feasibility of doing the conversion. Not the cost or merits of the 22WMR. I have a bunch of 22lr firearms, rifle, seemi auto pistol and revolver. I have no 22 mags. I have never found any use for it. If I go up from a 22 in rifles its a 223, a handgun I have a 22 jet, a 22 Harvey Kay Chuck. But, even before I had those I never wanted a 22mag.
 
rburg said:
I don't know what you boys are smokin' or drinkin', but I sure don't want any of it. Have you priced 22 mag ammo recently? So you're suggesting spending even more to convert a fine firearm to shoot a significantly more expensive round? OK, I agree its a free country. Freedom includes the right to be stupid.
Click to expand...

Yes, I have priced 22 mag ammo recently and there is lots of it available at less the $10 a box. Cheaper than a box of 22 LR was costing a couple years ago. And cheaper than the 22 mag ammo I bought nearly 15 years ago.

To the OP, there is currently a complete .22 K-frame cylinder for sale on GunBroker. Hope this info is helpful.
 
I had this thought many years ago. My K22, s/n K15xxx, was too precious to me to modify the cylinder, and I couldn't easily find a spare .22 WMR cylinder. So I bought a Colt Trooper Mk. III in .22WMR with a 4 inch barrel. Problem solved.
 
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