Disclaimer: I am not a gunsmith, just a humble gun owner with a technical mind LOL
I am an engineer and have an inquisitive mind. So of course, having gotten a new (new to me) CZ PO7, I took it apart
I am amazed at what is being done with polymers/plastics. Quite a feat of engineering. The engineer in me lets me marvel at the technology with no unfounded fears of plastics. Some people just don't trust plastic guns "give me steel".. well, I'm ok with it. I knew nothing of CZ guns or polymer guns going into this purchase. I found this forum, have read a lot about the issues, and the praises. My disassembly was with an eye to the 'issues'. First and foremost, I went right to the frame bulge. Yep, right side of my frame bulges a little. You know, I can go up and down the bottom half of the polymer gun frame and squeeze it with my fingers and move the plastic. The part that bulges, I believe, is due to the pressure of the one pretty strong little spring that sticks in there (you will be impressed herein with my technical jargon). I can push the bulge in, and it bounces back when I let go. I've concluded, as has been stated in other threads, that it is cosmetic. The top part of the gun - the chunky hewn of mother earth metal (argh argh argh) - seems to slide on two metal rails in the bottom half of the gun - two approx 3/4" long rails is all that holds the top to the gun. Pretty amazing. It's pretty obvious the bulging part of the frame plays no structural role insofar as high pressure loading while shooting. Where the explosion takes place is in fact quite the brick bleep house of metal-ness. I feel very confident that this gun is not going to blow apart at "the bulge".
Also, the two magazines that I got with the gun - yep, they always don't drop cleanly out. They don't stick to where I have to pry them out, but sometimes they pop out then hang and I touch them and they fall the rest of the way out. My old knock off 1911 45 does that too sometimes (it's all metal). The trigger pull on my gun seems great. This gun has been shot before - I can tell and the previous owner told me how may rounds he put through it. He says he had no issues.
Now, I encountered another magazine related issue. With an empty magazine inserted, I pull the slide back to locked open position. Fine. Then I eject the empty mag. As soon as I hit the mag eject button, the slide slams closed.. wth....
hmmm. Of course I had to figure out how the gizmos in there worked to accomplish the amazing technical feats of holding the slide open, retaining the magazine and all that. From what I can tell, the follower in the magazine - the plunger thingy that pushes the bullets up - has a shoulder on it that aligns with the small tab thingy of the slide release lever. When the last bullet leave the magazine, the plunger thing pops that tab on the slide release lever and lifts it up. That engages the slide lock back mechanism. And it holds it there until the shooter presses down on the slide release lever (in theory). So apparently, the simple act of inserting an empty magazine does not always fully engage this slide lock back mechanism. I haven't shot the gun yet to see if I have the issue under 'normal' use.
Anyway, just some first observations of this amazing little piece of technology called a PO7. Sorry if I have insulted the true gunsmiths out there and those that actually know how to describe gun things. Any input to my observed magazine issues more than welcomed.
