New handguard, now headspace problem

[Pauliedad]

So I took apart my relatively new Adams Arms upper to put on a Midwest Industries free float guard.
Pulled the BCG/handle, clamped the upper up in a jig, took off break,
knocked out two pins for low profile gas block, and took off original nut and delta ring.
Use new nut that comes with guard tourque it on pretty good, go a tad farther to line up piston and reassemble.
Throw in my no go guage and bolt closes. What gives?
I have put maybe 60 rounds through it prior, and I did not check it prior to pulling it apart.
What do I do?

Thanks, Paul

[ar15barrels]

New handguard, now headspace problem

Did you test with the no-go gauge before you did your assembly work?
I'm betting no...

What dimension is your no-go gauge?
What chamber do you have?
Do you even understand enough about the differences between 223 and 5.56 chamber dimensions to know how each gauge should behave in different chamber specs?

https://www.ar15barrels.com/data/headspace.pdf

It would be normal for the bolt to close on a 223 no-go gauge in a 5.56 chamber.

[Pauliedad]

Ouch,
I guess I don't understand the differences but will read up and look over your notes.
I was headed out of town just after I did the work so I won't be able to put my hands on that gauge till Sunday night.
Assuming its at .223 set, I should also get a .556 set?
I don't mind having more tools and appreciate being pointed in the right direction.

[ar15barrels]

If you look at the specific dimensions of the gauges, you will see what additional gauges you need.
If you have a 223 field, compare it to the dimensions of a 5.56 no-go gauge...

[yari]

Damn Randall do you even understand how harsh you were? Chill...

[kcstott]

That's not harsh thats frustration with someone typing a question without fully thinking about what they have for tools and what they have done.

I see Randal's frustration as this topic pop up about once a week to once every other wee and it's no Exaggeration.

And Please OP don't take my comments the wrong way. If you don't know you don't know. but this issue pops up very frequently.

Here's the simple point a .223 and a 5.56 are nearly identical on chamber dimensions but as you can see from Randal's page that the head spacing is very different/ and most 5.56 chambered rifles will close on a .223 no go. That is a NATO chamber

[Pauliedad]

No real butt hurt here.
I was aware of slight differences but did not even think about it when I ordered the go/no go set six months ago.
Being out of town is killing me right now in that those gauges may in fact be for 5.56 and I can't just run out to the shop and check.
I'm one of those that does a fair amount of research before I tackle something and like to be self reliant when learning something new but that does lead to the occasional oops.
My understanding at this point is that all should be fine and that changing the nut should not have effected headspace?
I will not shoot anything I've worked on without checking, re checking, and then checking again, headspace.
This was a case of I didn't know what I didn't know.
Sincerely, thanks for the guidance and will take whatever information you'd all like to share.

[kcstott]

No real butt hurt here.
I was aware of slight differences but did not even think about it when I ordered the go/no go set six months ago.
Being out of town is killing me right now in that those gauges may in fact be for 5.56 and I can't just run out to the shop and check.
I'm one of those that does a fair amount of research before I tackle something and like to be self reliant when learning something new but that does lead to the occasional oops.
My understanding at this point is that all should be fine and that changing the nut should not have effected headspace?
I will not shoot anything I've worked on without checking, re checking, and then checking again, headspace.
This was a case of I didn't know what I didn't know.
Sincerely, thanks for the guidance and will take whatever information you'd all like to share.

Very good practices to have.

As for the swapping of the barrel nut. As long as your mating surfaces were clean and burr free the barrel should have went back to the same spot (depth) on the upper as it was before with in .0004" or less I'm only throwing that number out there as nothing in the world ever goes back to zero. but it will go back to the same location with in a minor variance that is so small you would not be able to measure it.
I also throw out that example for the realization that QD scope bases and rings never return to zero upon removing and replacing. but in 99% of the cases they go back close enough.
so unless you have a burr or chip under the barrel extension shoulder you will not have any issues.

[ar15barrels]

My understanding at this point is that all should be fine and that changing the nut should not have effected headspace?

The headspace on an AR is completely controlled within the bolt, barrel extension ad chamber.
You can change bolt carriers, receivers, barrel nuts and not effect the headspace of a bolt/barrel pairing.

Check the illustration at the top of the headspace page as it shows how the bolt, barrel extension and chamber are all assembled.

[Pauliedad]

Thanks again, will do.