Bought a pin gage set to check cylinder chamber dimensions since I was having a tough time extracting fired cartridges from the K22.

First, here is the SAAMI sporting specs:
.22lr brass diameter: 0.226" - allowable tolerance - 0.004"
.22lr bullet diameter: 0.2255" - allowable tolerance - 0.004"
.22lr "base" of chamber diameter: 0.2307"
.22lr "throat" of chamber diameter: 0.227"
.22lr bore lands diameter: 0.217"
.22lr bore grooves diameter: 0.222"

Now, here is the SAAMI match specs:
.22lr brass diameter: 0.226" - allowable tolerance - 0.004"
.22lr bullet diameter: 0.2255" - allowable tolerance - 0.004"
.22lr "base" of chamber diameter: 0.2267"
.22lr "throat" of chamber diameter: 0.2248"
.22lr bore lands diameter: 0.217"
.22lr bore grooves diameter: 0.222"

I measured the following on the (very clean) cylinder of my K22, with the extractor in place and spent shells in several chambers. It was consistent in all 6 chambers:

"base" of chamber diameter: 0.226"
"throat" of chamber diameter: 0.224"

I think we can see what S&W did here.

Of note, my K22 extraction problems are unbearable with subsonic match ammo, merely very sticky with CCI std velocity, and nearly non-existent with hyper velocity velocitor CCI ammo. I suspect that the factory chambering works best with higher velocity ammunition as it is a higher pressure developed more quickly - exact mechanics of this are debatable but must involve brass expansion.

I have sourced an additional K22 cylinder and will be gaging it to cross-check another sample. I may end up reaming the new cylinder (non-SN numbered) to SAAMI sporting spec to make the gun usable with all ammuntion.

.22lr "base" of chamber diameter: 0.2267" (note: +0.002) (SAAMI Match)
.22lr "throat" of chamber diameter: 0.2248" (note: +0.002)

.22lr "base" of chamber diameter: 0.2307" (note: +0.002) (SAAMI Sporting)
.22lr "throat" of chamber diameter: 0.227" (note: +0.002)
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Your chamber measures 0.226 base and 0.224 mouth, but note that the SAAMI match chamber is also shorter than the sporting chamber by 0.175". You probably don't have a match chamber, and I doubt that there even is a match chamber for a revolver as there is for a rifle. No question your K-22s chamber is a little tight vs. SAAMI specs, but as the SAAMI case diameter tolerance is 0.226-0.004 (not +/-0.004), I'd think you shouldn't have too much of a fired case extraction problem. Are there extraction problems with every chamber and every ammunition brand? Can you tell how rough the chamber walls are? Have you tried cleaning the chambers thoroughly and possibly polishing them a little with jewelers rouge or other mild abrasive? I'd probably try a lot of things before I resorted to rechambering.

DWalt, you should consider that the SAAMI case dimensions are for unfired shells. Fired brass swells to fit the chamber, if there is no clearance it will conform to EVERY little nook and cranny. The chambers look good, and although they are not highly polished, my understanding is that this is undesirable as increases bolt thrust - which is a benchrest rifle shooting term but is also applicable here. I suspect you did not read my first post entirely as I addressed several of your questions already.

There is no chamber length standard on a .22 revolver. The chamber length is the length of the cylinder. In the case of a rifle or single shot pistol, the chamber length is the distance from the breech to the beginning of the rifling, and does have an impact on accuracy, thus the need for a spec. I don't know whether it is still true, but I believe that S&W once used a series of three reamers to form the chambers in their revolvers. They used a roughing reamer followed by a finishing reamer, and then finally a burnishing reamer. The Burnishing reamer did not remove any metal, but just sort of ironed the surface to achieve a very smooth finish. I can remember complaints about hard extraction on Ruger revolvers when compared to S&W, and you could see the difference in the finish of the chambers between them.

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Tom
1560

A search of this forum turns up a large number of threads on K-22s and model 17s with tight chambers. I don't know why S&W finished them this way but they did. I do know that the 17-4 that I have had since new has tight chambers and I suspect that the guns produced today by S&W are tight as well.

There are MANY posts here on this Forum regarding tight S&W chambers on their .22 Revolvers and many posts on people reaming them out with a finish reamer.

I have a bunch of Smiths and they are all tight where as my Colts have chambers that spit out the empties like greased lightening! I have to get around to reaming them - I did one M18 but have others to get to one day.

Yes, some brands of ammo are better than others but in general they are annoyingly tight. The M18 I did ream years ago is just as accurate as it was when I had to smack out the empties prior to doing it!

I have now reamed 7 different S&W .22's, J's and K's, both 17's & 18's. All of them had difficult to impossible extraction. They now all extract with just thumb pressure for up to and past 100 rounds. There was no change in accuracy.

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H Richard
SWCA1967 SWHF244

I may be speaking heresy, but if the reaming operation on the spare cylinder goes well, then I may just buy a .22wmr reamer for it, and use the .22lr reamer on the original cylinder....

Very interesting, I'd bet it works pretty well. Please let us know! Just be sure to use plenty of cutting oil, that's a lot of steel to remove.

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H Richard
SWCA1967 SWHF244