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.