Explain Headspacing - What it is, checking for proper spacing?

[popeye4]

Can anyone suggest guage sets? go/no-go/field?

Here: http://www.brownells.com/.aspx/cid=0...arch=headspace

Just don't mix brands (Clymer go, Forster no-go).

[Omega13device]

I've recently built two uppers (from a bare upper reciever, barrel, gas block, gas tube, handguard IT DID NOT COME PRE ASSEMBLED)

Again, the headspace is off the barrel extension so unless you're assembling the barrel and extension yourself, you're fine. But if you want to measure it anyway, knock yourself out.

[FatalKitty]

ideally the bolt and extension on new parts will be within a certain spec and should NOT need to be checked when assembled. If you are using used parts then sure, check it out.

never checked any of mine that I assembled - I did however keep an eye on the spent casings for signs of excessive or lack of headspace.

[SanPedroShooter]

As a reloader, I understand the concept of headspace (sort of...). I also know how to check and read brass for weakness and firing issues. Checking headspace after wear and tear on a barrel and extension before throwing in a new bolt is a good idea. My upper was built and test fired by LMT. I am going to trust them on this one.

Off topic:
Anyone who wants to really understand firearms, needs to load their own ammo.

[CHS]

So I'm going to remove the extractor from the bcg. throw it back in.

You need to remove the ejector as well, which requires a small roll pin punch.

Also, if you're buying a brand new bolt and barrel, checking headspace is likely going to be a big waste of time and money.

Check your headspace after your first 5000 rounds and THEN get back to us.