1. Check out the mag well. One way to easily see if it is well used sort of it to check the mag well. Someone like me who does a lot of compittions and reloads has chewed up mag wells since they are polymer.
2. Check the outside. Lookover the frame and slide. Are there any major scratches or cracks. One to look for is the disassembly lever scratch it is the most common. BAsically some one pushed the disassembly lever into the slide and it has a nice scratch going some of the lenght of the slide. Look for cracks in the polymer although dont confuse them with the molding mars.
3. The rear of the slide. Look at the round plastic piece...the firing pin spring guide. Look at the hole is it round or is it oblong if it is oblong it can be fixed but thats in dindication you status indicator is off and may break soon. It wont impeed the function and can easily be replaced.
4. take the slide of the frame. During this check to see if the grip safety works. check to see if the trigger safety works. If they wont let you see the insides...me personally Fu@k um they obviously did not want the sale.
It is safe to dry fire the pistol.
5. look at the frame. Check out the locking block is it chiped along the front edge where the barrel sits. Is it clean?
6. Look at the rear assembly of the frame. First look at the polymer rails, there should be no wear marks at all infact you should actually be able to see some machine marks. If there is wear or it is chewed up in any way walk away. I have several xd and hs2000`s with several 10`s of thousands of rounds and they dont even show rear frame rail wear. It is an indiaction of some medeling but just trust me walk away.
7. Look below the polymer rear rails at the round holes are they round if so good if not walk away. Check the sear do it look normal or did someone polish it up real nice all over (home trigger job walk away) or obviously took a file to it. The rear of the sear should be even and have a sharp top rear.
8. Lift the slide stop all the way and let it go...it should snap back down with authority.
9. Check the trigger. With the frame only grip the pistol as if to shoot it and give the trigger some slow methodical pulls. It should be smooth and not gritty. With the trigger pulled all the way back push down on the disconect. Thats the hump on the right side push it strait down the sear should pop back up this is good. Then slowly relase the trigger you should hear a small snap thats it reconnecting now pull the trigger the sear should move back down.
10. Check the barrel. First look at the lugs on the bottom are they chewed up? Check the feed ramp is it smooth at least. Too smooth and shiny could be a home polish job and they could have messed it up....this is your call. Now check down the barrel how are the lands and grooves? Is the barrel bulged or at any way odd looking. One way to check the amount of cycling is to look at the front top of the barrel the less wear the less the pistol has bee cycled. dont worry if there is wear they all show alittle even after a few hand cycles.
11. Look at the bottom of the slide push in the firing pin saftey the oval object under the slide. While the safty is pushed in push the firing pin forward. then let the safety go. The safety should be holding the firing pin forward (this lets you know the safety`s spring is strong enough) now while the firing pin is forward look at the breech face is the tip of the firing pin sticking out? If so good its all in there.
12. look at the top of the slide. with your finger lift up the loaded chamber indicator and let it snap back down it should go back down with no problems. Now look further back on the slide at the hole. Inside is a roll pin that is in the shape of the letter"C" the more it is all chewed up means some one has had the slide appart.
13. Look at the sights there are centering lines on both the front and rear do you see all four lines. If not the sights are not centered a consideration if you dont have a punch or the time/knowhow to fix it. Also an indication that A. an amuturer put them on or b. the sights are loose and will need some lock tight so they dont move.
14. Look at the underside again at the extractor. Look at the claw of the extractor is there alot of gunk in the claw? It should be clean. Is the claw chipped thats a bad thing. Look allong the length of the extracot under it are there scratches? If so it means some one tryed to take it out.
I could go on and on but this should more than get you into trouble.