I actually got this PMR from a buddy that bought it when they first came out. He was on several wait lists and one of the newest gens came available so I got his older one. The difference between the gen I got and the one he got is mine has a fluted brl which Kel Tec has done away with for manufacturing speed reasons, my mags are not drop free when empty, and my frame is a bit less tacky to the feel. I put some rds through this pistol when it was my friends but not since I have acquired it.
As to the mag over the .22lr in a pistol, there is ammo that is formulated for the mag in pistol length brls that push more FPS. I like the advantage of 30 rounds too. If the rumor of a PMR-30 in .22lr materializes I will get one of them too. As a side note from shooting objects with a revolver in .22lr and .22mag the mag does a lot more damage. My brother had a SAA in .22lr/mag combo and the mag punched through things a lot better--unscientific but that is how the guys did their test in the old days (ask pigs and horses).
The short barrel of a handgun does cost a lot of velocity (in 22Mag trim), but there is still more "power" in the Mag.
I've had a couple of Ruger's Single Six's with the 22LR and 22Mag cylinder swap option. I didn't fire a lot of 22Mag due to the unreasonably high cost of that type of ammo, but my very informal tests yielded fairly dramatic performance differences. The Rugers I had were 5.5" if memory serves (this was a long time ago).
I've owned MANY 22LR ...rifles... over the years, and a couple of 22Mags. In a rifle the performance is VERY noticeable. I currently have a CZ452 Varmint in 22Mag for coyotes on my property and a couple of 22LR for everything else.
For rimfire handguns I prefer Ruger's semiautos. I've owned a bunch of rimfire handguns over the years. Here are a few that come to mind:
* 1911 Conversions
* Browning Buckmark (several different configurations)
* Colt Target Model
* Jennings J22
* Phoenix HP22
* North American Arms "Mini Revolver"
* Ruger 22/45 (several different configurations)
* Ruger MkII (several different configurations)
* Ruger MkIII (two configurations)
* Ruger Single Six
* Sig Sauer Mosquito
* Smith & Wesson 17
* Smith & Wesson 18
* Walther P22
* Walther PP
* Walther TPH
There are others, but these came to mind easily. The only 22 handgun I own now is a Ruger MkIII. Its accurate, reliable, and well made.