The 22/45 is the cousin of Ruger's Mark II .22 pistols. It is a blow back automatic loading pistol, using the force of the recoil to move the bolt. It uses practically all of the same parts, except that the magazines are slightly different, in the buttplate; the big difference is the frame. The 22/45 uses a molded plastic frame, while the Mark II has a metal frame and detacheable grips. The cost of the blued bull barrel version was $210.
The 22/45 I got has the bull barrel, which is nicely heavy and is apparently supposed to mimic the feel of a 1911 style pistol, although I don't know, I haven't gotten one of those yet. The gun is a bit barrrel heavy, balancing a bit forward in my hand, but overall feels quite nice. It has a solid, massive feel to it.
At the range, I was surprised at how well I shot with it. My best slow, carefully aimed ten shot group (one magazine) measured about two inches, with the exception of a flier way out in the 8 ring, nicely centered on the X. This was at 50 feet at an NRA 50 foot pistol target. I consider myself a novice, and usually I don't get anything nearly that good with my .357. While one would expect .22 not to be much of a thrill, it does have a definite recoil, muzzle flip, and report. It was not, as I was afraid from people warning me, "wimpy". In fact, it was a lot of fun.
The gun does have some drawbacks. First, it is impossible to change the grips, as the 22/45 has a one piece molded frame; I intend to write to Ruger and ask that they change that. The other problem that I have, which bothers me quite a bit, is the bolt release button. To release the bolt from its open position, after clearing the gun or after shooting the last shot, requires a lot of downward force on the button, that is, down towards the butt. It is actually a lever with a button like end. I am not sure why this is, after taking the gun apart my best theory is that the surfaces of the bolt and the lever face are still somewhat rough, where they meet to keep the bolt from closing. Perhaps with use it will loosen, but right now the only way that I can close the bolt without changing my grip on the gun is to pull the bolt back about 1/16 and at the same time push down on the lever with my thumb. I did not find reassembly to be as complicated as the gun store salesman told me it would be, the manual explains quite clearly what to do.
Overall, I am quite pleased with my purchase, and I would recommend it as a plinker/cheap practice gun, with a caveat on the bolt release.