Well first test results are in on the KAK 22TCM barrel and unfortunately they are not great.
The first 10 or so rounds had really odd behavior in that the rounds would not even eject. At first I had the full sized CF tungsten bolt in the gun and the first two shots the rounds were so stuck in the chamber to the point where they had to be hammered out with a cleaning rod.
I switched to the lighter OEM steel bolt and things improved but ejection was really anemic (barely dribbling out of the ejection port) and I was getting sporadic FTE behavior. I probably had about a dozen rounds down the barrel when I decided to go and clean the chamber with cleaning brush, followed by a couple strokes of a 22 cleaning brush, followed by some hoppes patches to see if that would help.
After a bit of barrel cleaning the steel bolt and barrel started to work better but over maybe another 25 rounds the rate of fire sped up to what I would guess was starting to approach 2000rpm. It felt like there was a Mac Jack block installed in the gun when running 9mm, throwing brass really far, and it quickly got to the point where primers also started distending and/or popping out of the cases. Reliability to feed was also not good with many FTFs resulting in both cases and/or the nose of the projectile getting a bit mangled in the process. I saw some minor neck swelling as well but nothing like the posts above and no case separations, etc.
However, after a couple primers fully unseating themselves I called it a day for the steel bolt and switched back to the full size tungsten CF bolt to continue testing.
The CF full size tungsten bolt stopped the primers from distending or completely unseating themselves and the case necks looked just fine out but my shot timer clocked the rate of fire between 1100 and 1200rpm.
It felt speed wise almost identical to shooting the 9mm gun with the steel bolt but more of a recoil impulse given its 1100ish RPM with a 2.5X weighted tungsten bolt going back and forth and which is clearly impacting the rear of the receiver. I also had a lot of failure to feed issues with cases getting mangled or the bullet nose jamming into the edge of the barrel. Overall from a feed perspective Zytel mags worked much better than ZMags, but even the Zytels were spotty. The Recon Ordnance PAM-2 mags were just a complete no-go as every round ended up getting driven into the top edge of the barrel. I do plan to may try and tweak some Zmags or Recon mags feed lips to see if I can get the feed angle a bit better and resolve the FTF issues.
My takeaway is that the barrel out of the box must be really rough on the interior of the chamber and that was initially keep the rounds from ejecting and they would expand and glue themselves to the rough chamber interior. As the rough park or coating, etc. was worn in and smoothed out the ROF then sped up dramatically.
IMHO, the OEM steel bolt doesn't appear to have enough mass to safely shoot this cartridge in an open bolt SMG. Maybe in a semi with the weight and spring of the hammer it works OK. However, it appears at a minimum it looks you need the full size CF tungsten bolt and even then I am skeptical on the wear and tear on your receiver with a full sized tungsten bolt going back and forth at 1100rpm. Given the number of failure to feed issues you are also probably risking an out of battery at some point if/when the firing pin finds itself into the primer with the round not fully chambered.
I plan to do a bit more testing at the range later this month as I still have a decent amount of ammo. However I want to put one of the softer/thicker Lage neoprene style buffers behind the full size CF tungsten bolt vs. the thin rubber one I have in there now given the recoil impulse. I also still want to try the Tungsten A bolt with a really nice thick buffer to protect the receiver. I also ran out of time to chrono anything but will try and get that done as well.
At this point unless you want something to troubleshoot or tinker with, I would be hard to recommend buying one of these barrels and expecting it to run out of the box.
Hope this helps