Need your help with headspace.

[LoadedDrum]

I wanted to check the headspace of a new barrel and bolt combination on an AR I had just put together so I purchased a set of Clymer Go and No-Go 5.56 headspace gauges from the CMP. I removed the ejector and extractor and reassembled the BCG minus the above parts. I put the Go gauge in the chamber but the bolt will not close. The chamber is clean and the bolt and barrel (5.56 chambered Armalite) are brand new. Just to see if I had a short chamber, I tried the same Go gauge in another AR (with ejector and extractor removed) that has a round count of about 500. It will not close on that one either. Finally I tried it on another rifle with 2900 rounds down the barrel. It will not close on that one either. FWIW, I have never had a problem shooting either of the rifles that have been fired. What does this mean and what should I do?

Also on an unrelated issue, I have an AR with a bolt catch that will not hold the bolt back manually. I changed both the spring and the catch itself but nothing helped. Any suggestions?

 

[nicholst55]

So, neither bolt will close on the 'Go' gage? That is unusual. Do you know anyone else with an AR or other .223 rifle that you can try the gage in?

I'd try that first, and if you are unable to find any rifle(s) that it will close on, I'd be on the phone to Clymer. I'm wondering if they mismarked this gage, and it should be labeled as 'No-Go' or 'Field.'

 

[ieszu]

I believe there is a slight difference between .223 and 5.56, that could be the difference. Its similar to the whole .308 and 7.62x51 issue... there could be a thousanth or so difference at one point on the case...

You might just want to make sure

 

[frogomatic]

+1 nicholst55 - you probably have a miss marked gauge.

the bolt cathc problem is more likely to be magazine related.

 

[Jim K]

I would see if I could find a gunsmith with a known good GO gauge. If the rifle really dosn't accept a good GO gauge, it doesn't mean the rifle won't function, only that if you run into some ammo that is on the long end of the ammo spec, you will have chambering problems.

Jim

 

[LoadedDrum]

So, neither bolt will close on the 'Go' gage? That is unusual. Do you know anyone else with an AR or other .223 rifle that you can try the gage in?

I'd try that first, and if you are unable to find any rifle(s) that it will close on, I'd be on the phone to Clymer. I'm wondering if they mismarked this gage, and it should be labeled as 'No-Go' or 'Field.'

I have a Forester 1.4636 Go gauge on order. Hopefully that will work. I have also e-mailed Clymer just to see what the measurement of their Go gauge is supposed to be.

 

[LoadedDrum]

The bolt closes on the Forester gauge so I am sending the Clymer gauge back to Clymer so they can see if it is mislabled. Thanks to all who replied.

 

[LoadedDrum]

Update

I received the gauge back from Clymer. It was mislabeled. They corrected it to 1.4636 and now it is marked as such (the gauges do not come with a measurement printed on them. It now closes as it should. Thanks to Tammy and Todd at Clymer.