ar 15 parts gun

going to a small local gun show tommotow and i know that a local gun shop will be there selling ar15s . my question is how can i tell if the gun is assembled from parts if the upper and lower are the same make? serial # ? the reason i ask is that the guy usualy has some good deals but he has been known to build an ar and the sell it as new from factory .. i know i shouldnt even look at his stuff and i should wait for the fort wayne show later this year , but if i see a good deal i would like to know if he is trying to screw me
thanks

Well it's a tough question. Most AR platform guns are "parts guns". The S&W is a parts gun. They just don't advertise it. Regardless of the brand most lowers are pretty safe. As for the parts kit used in them it varies. The upper may be complete from a manufacture or assembled by someone else. I would ask him questions about twist or if it's marked 5.56 or feedramps or markings etc.. It really depends on what you are going to do with it. A bare bones lower line bushmaster might be fine for you. Or if you plan on shooting more than a couple thousand rounds a year you might want a LMT. What kind of price range do you want to be in?

thats what i was thinking ... the gun will probably see around 800-1000 rds a year
and my budget is in the 800-1000 range
am i crazy for thinking about building my own .
never owned one before , but when i get one i'll do full teardowns for cleaning and inspection
been looking at colts and lmt so far .. any other suggestions

The next Fort Wayne show is in April. I have gone to several of the shows and don't think there are "big" deals there.

You may be better off just checking around gun shops. H&H normally have good prices and so does Ranger Supply who specialize in AR’s and tactical gear.

Grant at G&R is one of the forum dealers here. He's great to deal with and i'm sure he could ship to your local dealer for a transfer.