The bore light idea is a good one, and in the absence of that-keep in mind that gun dealers (in many cases) respond with, "probably a few hundred rounds." They seem to repeat that phrase like it's against the law to guess otherwise.
1. Check the wear around the corners, and trigger guard. The problem is that the wear may be more about holster wear than actual firing of rounds.
2. With semiautos, they are often checked (for wear) by exercising the slide, and other parts that move-without dissasembly. They will get more loose/sloppy with greater use. It takes time to understand the difference between light and moderate use if a pistol is really cared for, and not showing age on the stainless, or bluing.
Note 1: A dealer does not want to remove a slide in some cases-unless you are interested in buying 'that' pistol. However, I've found some sales guys that do it, like they're bored, and like to show how familiar they are with the guns for sale. YMMV.
Note 2: If you press the slide release (empty), and let the slide "ker-chunk" forward in the store, you might be shown the door. Think of it this way, at the range, you release the slide and a bullet is chambered. The parts are not working too much in that instance. However, in the store, with it pistol empty of bullets, you putting unnecessary wear on the slide/frame by letting it slam forward-empty. Don't!
If you haven't learned to put your other hand above the slide and help it forward without letting go, take a lesson from the salesman. This lets 'you' move it through the paces without fully releasing the slide, and it will prevent upsetting the guy behind the counter, or his boss!
Have fun evaluating pistols, and be SURE to share more about your purchase-when it happens.
