Anything special I need to look for when buying a complete ar upper w/ BCG?

[PeaShooter]

I am looking at a couple of used uppers and was wondering if there was anything i needed to watch for. i.e. wear, headspace, etc.?

 

[mkbar80]

If I was buying a used upper I'd do the following...I'm also curious to see what others might suggest, I'm sure there is something simple I'm leaving out...

BCG
Look for any obvious knicks or broken off corners on the bolt lugs.
Extend the bolt and stand the BCG up on the bolt, it shouldn't collapse easily under its own weight, if it does the rings are worn.
Take off extractor and check to see if its still sharp, if you pull it over your skin it should leave marks.
Make sure key isn't loose and it's staked well.
Anyone have a simple way to check the ejector spring outside of loading loose/dummy rounds??

For the upper
Look down the bore to check for any obvious problems
Pop off the handguards if you can to see if the gas tube is beat up/misaligned/etc.
If you can, borrow a set of go no go gauges for the proper chamber (5.56 or .223) that would help.
Make sure charging handle isn't bent to **** and that it latches properly.
If you have your lower I'd bring it and but it all together and run a function check.

If everything is on the up and up and the extractor/rings/springs etc is just worn you might just see if the guy will knock $50 or whatever off the price and you can order those items from BCM or elsewhere for less than the $50 bucks. An entire bolt can be had for under $100.

 

[mvician]

How much you going to save by buying used?
With the price market of ARs today, it really doesn't make much sense.