The Gamo PT-85 Blowback on review is a CO2-powered semi-auto .177 DA/SA pellet gun with "blowback" feature -- i.e. the rear portion of the slide moves back on firing to cock the hammer. While this does mean that shot count per CO2 bulb will be lower, since part of the pressure produced by the CO2 expansion in the valve is used to move the slide, the pistol still has plenty of power, spitting out medium-weight pellets at around 450 fps, or just under 4 fpe -- more than enough for plinking, or putting down trapped rats.
It uses a plastic magazine carrier with twin, rotary, eight-shot magazines, one at each end, so you get 16 shots without reloading -- you simply slide out the mag carrier and reverse it. In 15° C ambient temperatures, I get about three mags (54 shots) per 12oz CO2 bulb. The first 40 shots are consistent, after which the power starts to drop off. Output will be slightly higher in warmer temperatures.
Here's a typical target, showing a sub two-inch eight-shot group at right, from five metres. At left are my first attempts to find POA. The right-hand group was shot aiming at 6 o'clock on the bottom of the right-hand bullseye circle at that range. I'm guessing that at 10 yards/metres, or maybe 15, POA would be at the centre of the bull, but that's for another day.
The trigger is fairly heavy in double-action, but quite light and predictable in single-action. You can cock the slide or pull back the hammer before the first shot, and shoot all shots single-action. The blowback feature is pretty realistic -- it's reminiscent of the action on my Browning Buckmark .22LR, which has quite a beefy slide. It does move the pistol around, though, so a two-handed grip is best.
The pistol is solid and weighty, with some heft to it, which helps with accuracy. The grips are plastic, but feel OK in the hand, and provide good traction. There's also a front rail under the barrel for a laser or torch mount. It seems to function well with wadcutters, pointed and domed pellets in the 8.5-grain range, although some heavier, magnum pellets would probably be too long to fit in the magazines.
As a backyard plinker, it does what it says on the tin. Most importantly, it's fun to shoot, so no plinking target is safe.