A friend of mine loves his KT PMR pistol and CMR carbine.
30 rounds of 22 Mag, interchangeable mags.
But rimfire reliability would always be an issue.
I had an early PMR 30 but it was a picky eater. CCI maxi mags or V mags were the only rounds you could use to avoid FTF issues. It throws a 12 inch muzzle flash and is louder than a you know what. Maybe the newer models have the bugs worked out. I sold mine and got a Ruger SR22. Much more reliable. But Keltec makes a lot of interesting stuff.
I have both. They are awesome. They work better with heavier bullets.