when installing a new barrel on a upper receiver. Is it nesseary to check the headspace with a go no-go gauge if the barrel, barrel extention and bolt are all new parts. i was under the assumption that the only issue that could arrise is just an out of spec chamber since there is no way to adjust the actual headspace. Im i correct in my thinking???? If going with all quality items such as a wilson barrel and extention whats the liklyness ill run into a problem? The issue is the gauge may not be availible to use when i get the barrel swapped.

You are correct.  You are using good parts, checking not necessary.  Put it together and shoot.

Quoted: You are correct.  You are using good parts, checking not necessary.  Put it together and shoot.

Hmm, really?  

My LMT upper and bolt are probably fine, but I'm still nervous.

The only need for head spacing is if you are putting barrel extensions on, and most people arent. if you are putting a barrel on an upper receiver, no head spacing required.

Making sure I understand here....
the head space is based off of the barrel extension and the bolt.
Changing the barrel has no effect on it as long as what you have is good quality components.
Hope this isn't too dumb of a question but does anyone mfg/sell an upper that does not have a barrel on it but has all the other stuff , bolt/carrier group, barrel extension,etc...
In case say that they did n't have a particular barrel you wanted or just wanted to do as much of the assembly yourself as you could.

How exactly is the headspacing set on these new rifles ?
(just trying to learn here)

Head space is set in the mfg of the barrel.

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"In over 20 years I have never found one that didn't pass with flying colors."

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