I've got a new unused Colt barreled upper originally made for the M16A1.  Unfortunately it is missing the bolt assembly.  I need a complete AR bolt carrier assembly.  I'm wondering what my concerns should be with headspacing a new bolt?  Would my chances of achieving proper headspace be better if I were to look for a Colt made bolt assembly, or should any USGI spec bolt assembly heaspace ok?  

I'm an M14 guy so I'm trying to get up to speed on the AR world.  Thanks!

usually new parts from any manf.  will headspace fine.  the only time there may be aproblem is if the factory screwed up the install on the barrel extention.  or the bolt is out of spec.

of course, when it comes to your hands/eyes/cheeks/ears, did you want to trust someone else's work?  i would suggest you pick up a set of headspace gages from brownells and check it out.  

you could probably build 100 ARs out of mis-matched parts and never find one that didn't headspace.  but when you build #101 and it doesn't... you will wish you had checked it.

Originally Posted By Doctor M14: I've got a new unused Colt barreled upper originally made for the M16A1.  Unfortunately it is missing the bolt assembly.  I need a complete AR bolt carrier assembly.  I'm wondering what my concerns should be with headspacing a new bolt?  Would my chances of achieving proper headspace be better if I were to look for a Colt made bolt assembly, or should any USGI spec bolt assembly heaspace ok?   I'm an M14 guy so I'm trying to get up to speed on the AR world.  Thanks!

Nice upper.
Buy one.
Check headspacing IAW the manual.
The biggest difference between a Clot bolt and "any of the others" (with a few exceptions) is the Clot bolt will be more expensive.

10 to 1 there is a chance that the same company that makes the Clot bolts also makes "the other guys" bolts.

Clot bolts are "for the most part" the ones that are more uniform as far as them meeting the Mil-Spec requirements.

There is no such thing as a "Mil-Spec" AR15. If you were to buy a "Mil-Spec" Clot bolt/carrier assembly it would be known as an M16 bolt/carrier assembly.  

Buy an assembly from Colt, Bushmaster, Armalite, LMT, Oly, then check headspacing.

Headspacing post.....
www.ar15.com/forums/forum.html?b=3&f=4