Are brand new barrels and bolts from the factory headspaced?
I ask this because I will be buying a new upper from at the gunshow this weekend.  The dealer sells his uppers with or without bolt/carrers I don't know if he sells them as complete uppers or uppers without bolts.  If they are sold as complete then I don't have any headspacing worries but, if he just pops out the bolt then sells them then I'm wondering if I should have the headspace check

thanks for the help

If the barrel is part of the upper, then yes, it **should** already be headspaced.

If you're buying a barrel w/o the upper, then it'll have to be headspaced to ensure safety.

You can swap bolts from upper to upper w/o a safety concern. There will be some wear differences though.

Huh??? The upper has absolutely nothing to do with the headspace on an AR.  Headspace is controlled by the locking lugs on the bolt head, and the corresponding lugs inside the barrel extension. You can cheak the headspace with nothing more than a stripped barrel, a stripped bolt head, and a guage[:D]

The head space is not affected by the barrel not placed properly in the upper?

It's damn near impossible to put a barrel into the upper incorrectly, without distorting the upper so badly the whole piece would be inoperable. The only two screwups that wouldn't leave the whole thing a wreck would be 1) improperly supporting the upper and barrel so that the indexing pin on the barrel digs into the left side of the index channel on the upper, and 2) undertighterning the barrel locking nut so much, that the whole assembly stays a bit loose.

Item 1) will give you excess right windage, and you'd have to use a lot of left windage adjustment to center groups. Number 2) will ultimately give you lousy accuracy; from the barrel minutely shifting in the upper during each shot.  Niether will give you excess headspace[:D]

BTW, four of my six ARs are equipped with GI surplus, Colt made, Viet Nam era bolt heads (the other two are original Colt bolts in their original Colt barrels). All of them mike out well under max, despite having over 30 years of use in their original rifles.

Why did I opt for used pieces? Two reasons. Firt, the price; $15 apiece complete. Second; I know Colt built them right, and while the aftermarket folks use good materials, my experience is that they don't micro polish them, resulting in sharp edges that shave brass chunks off the rear of the case, ultimately tying up the rifle; and sometimes the knife sharp edge of the cam pin hole causes the bolt to crack at that point.

Bob, the upper has no affect on headspace.  The only parts involved are the barrel assembly (barrel and barrel extension, which for end users is one part) and the bolt.  That is all that affects headspace.  

The upper receiver is meerly a part that ties it all together, guides the bolt carrier.  In the AR15/M-16 design, the bolt locks into the barrel extension.  This is not like a bolt action, where the bolt locks in the receiver.  

Bolts made to spec and barrels made to spec are already correctly headspaced.  Go on and check headspace, but it is not adjustable by anything the assembler will do to it.

Ok, more lessons learned.    [}:D]