My local dealer just got a used S&W M&P Shield in as a trade in. It is in 9mm. Im interested in it.

Can someone tell me what to look for on this used gun to ensure it is mechanically good? Are there any things in particular to the Shield line that I should check?

Supposedly, and this is what the dealer is saying, the guy bought it, kept it a month and returned it as a trade in on a Glock because he really wanted a Glock. Also, he told the dealer he only fired one full magazine through it. Hard to tell if that is true. The feed ramp and chamber are black with soot, but the end of the barrel doesnt have much wear at all when I retracted the slide. The outside appearance looked good.

Thanks for any advice! Oh yea, they have it marked at $419.00 but I will offer him a lower price, they usually work with me on prices!