As this is my first foray into a decent CO2 air gun, I thought I'd do a bit of a review. The OP might find this useful!
I recently bought a Umarex Gloc 17 Gen 4, and just finished shooting it for the first time. I have to say I'm pretty impressed, both with the gun, and with it's realism and accuracy.
I had a real Glock (model 22 Gen 4, although functionally identical to the 17 except for caliber - I also carried a Glock 22 Gen 4 at work daily, for many years, so it's as natural to my hand as can be), and this Umarex is an incredibly accurate copy. It is a blowback (although with reduced recoil, of course) which enhances the shooting experience. I moved to Mexico in October, so couldn't bring a single one of my real firearms with me. As a gringo, legally obtaining a pistol here is extremely difficult (and maybe impossible). I've been itching to shoot again, and I loved my Glock, so this seemed a pretty good compromise.
It's an official Glock-licensed copy, with a steel slide and polymer frame, like the original. The engraved markings are genuine Glock throughout, and the Glock safety trigger functions exactly as the original. The mag even has the markings for the number of rounds, and the slide locks open after the last shot. If I put a real Glock 17 Gen 4 in one of your hands, and the Umarex in the other, you could NOT tell the difference. The ONLY clue that its not real is the smaller-diameter, recessed functional barrel, hidden somewhat inside the muzzle of the actual-sized (but non-functional) 9mm barrel. Of course, it fits all real Glock holsters, and the mag(s) fit real mag holders. Extra mags are VERY expensive here, though.
I'm getting about 54 full-power shots per CO2 cylinder, and then the CO2 dies off quickly. The mag contains the CO2 cylinder, and holds up to 18 steel BBs. Three full mags pretty much uses up a CO2 cylinder.
CO2 cylinders and BBs are cheap & readily available here, so I can shoot as much as I like in my garage, which is about 50' across although I've been shooting much closer so far, until I get used to the gun. I want to keep the BBs in my homemade trap (a Tupperware tub, with a hanging towel inside which catches and drops the BBs inside the tub), and as I gain confidence in my ability to do that I'll keep moving back.
I'm getting used to the sights, which are different from those on my real Glock 22 (it had the Trijicon night sights installed at the factory), so my first shots were a bit low, but the grouping was surprisingly good, just a bit low (my first couple of shots were mag dumps, of course!), but once I concentrated on getting a real sight picture the groups were right on the money. Considering this is a blowback CO2 gun, I'm pleasantly surprised at its capabilities.
If I had known how good this copy was, I'd have bought one when I owned my real Glock. It would have been great to blaze away at home, for cheap, fun practice.
Here's a link:
https://www.replicaairguns.ca/glock-17-4th-gen-177-cal-bb-pistol