I am goin to a gun show next weekend and I m thinking about buying an ar while there. it will be a base for a 16 inch home protection weapon. while it will not be my first ar I was just wandering if any of you guys have any tips about things to watch out for. thanks in advance guys

If you buy new, you're likely ok.

If you buy used... obvious stuff like excessive wear, etc.  If they won't take apart and let you look at the innards, don't buy.  If the guy looks like he's fly-by-night, he probably is.  If you ask the guy where he's from, and he simply says "Houston" and you're in Houston, TX, and you look at the address labeling on his wares and he's from Houston......... MO (like those shifty motherlovers from A-1 Guns of Houston, MO, at the last HGCA show... who I reported to the HGCA for misrepresentation), don't bother... i.e. standard gun show stuff.  Basically, if they look shifty, they probably are.

However... especially for ARs, be careful of undocumented pre-bans.  If you are going to buy a pre-ban, make sure the guy has all the proper documentation in order to prove to you that it's a legally configured pre-ban rifle.  If he cannot provide this, don't bother, no matter the rifle or price.  It's not worth the potential hassle down the road.

I've seen new AR's that were suppposed to be factory built complete firearms, but appeared to be upper kits built on a "name" lower, but offered for sale as the "name" firearm built completely by the manufacturer.
Look for marks where rolls pins installed, etc.  Also do a little homework before you go to see what configs the manufacturer offers.  If something doesn't match the factory configs, probably not quite right. If it's a local dealer and you purchase, you can always check with manufacturer to see if it left their factory as complete, or just lower.
Build your own, and then there's no doubt about the parts.  BTW, I'm primarily refering to post bans.

If you are looking for a preban then download & print this serial number list & take it with you so you won't get burned!!

old.ar15.com/legal/serialNumberList.asp

ColtShorty

GOA KABA COA JPFO SAF NRA

"I won't be wronged,  I won't be insulted
and I won't be laid a hand on. I don't do
these things to other people and I require
the same from them."

Quoted:
If you are looking for a preban then download & print this serial number list & take it with you so you won't get burned!!

old.ar15.com/legal/serialNumberList.asp

This is the best advice I've seen.

I got the old switharoo at a gunshow years ago..I saw a BM shorty asked how much..did the deal and later I got home and pulled out the weapon..was a A1 upper not the A2 upper I had handled and purchased/wanted..was also missing the mag..called the guy who later claimed I should have checked it...I saw the gun go into the case, but he did lay it on the ground behind the table to put in in there..I got a decent deal buy I was really pissed...After talking to this vendor it was real plain to see it was a scam...I kinda think of the dealers/vendors at gun shows as used car salesmen..should be a nice buying experience but in the end it aint...I buy from arrogant local dealers now...