new mega build fails go gauge but champers round?!

[cjlane]

So I just finished a Mega MATEN build. I have DPMS bolt, Mega 20" barrel.
I remove the ejector and test the head space with foster go/no go gauges.
I tried the GO gauge first by placing the gauge into the chamber and the bolt would not close all the way.
I then put the GO gauge into the bolt and then pushed both into the receiver and the bolt would close all the way.
I then tried the latter with the NO GO gauge and it would not close all the way.
Lastly, I loaded some 308 rounds into a magazine and manually cycled the round and the bolt closed all the way and they ejected just fine.


What is going on here where the GO gauge will not allow the bolt to fully close when I place it into the chamber VS. putting the gauge onto the bolt (held by the extractor) and the bolt closes?
I have the forster gauges - some people remove the extractor and some dont and it does not seem to effect their outcomes.

I just tried again with the extractor removed as well and the GO gauge passed by just dropping it in and the NO GO also did not close

 

[George63]

"I just tried again with the extractor removed as well and the GO gauge passed by just dropping it in and the NO GO failed."

you answered your own question - also after a 1000 rds everything will loosen up

 

[cjlane]

Yeah, I figured as much. It is my first build so I was expecting the worst when the GO wouldnt chamber the first time.

 

[-Nick-]

Just an FYI but on some the No-Go will also close. It's the field gauge that should NEVER close.

 

[LoneWolfUSMC]

Just an FYI but on some the No-Go will also close. It's the field gauge that should NEVER close.

This.

If the barrel was chambered to accept .308 and 7.62NATO then it may fail (close) the .308 no-go.

In our MATEN build series I went into detail on checking the headspace.

 

[Strykervet]

I read the same question about the same build on the gunsmithing forum yesterday or day before. But I think you got squared away --the extractor on the AR will cause some resistance. I guess Mega recommends drawing the bolt halfway back and letting the recoil spring close on the gauge. Doubt this is great for the gauges though.

You should look up that thread, it had more info on it anyway.

 

[cjlane]

Thanks for the follow up guys. So was my only problem that I didnt remove the ejector AND extractor the first time? Or should the extractor not be a factor and something could still be out of spec?

 

[cjlane]

I read the same question about the same build on the gunsmithing forum yesterday or day before. But I think you got squared away --the extractor on the AR will cause some resistance. I guess Mega recommends drawing the bolt halfway back and letting the recoil spring close on the gauge. Doubt this is great for the gauges though.

You should look up that thread, it had more info on it anyway.

Thanks Ill look into that

 

[-Nick-]

Thanks for the follow up guys. So was my only problem that I didnt remove the ejector AND extractor the first time? Or should the extractor not be a factor and something could still be out of spec?

Right now your problem is you're not reading what was said earlier...

This.

If the barrel was chambered to accept .308 and 7.62NATO then it may fail (close) the .308 no-go.

In our MATEN build series I went into detail on checking the headspace.

 

[cjlane]

Right now your problem is you're not reading what was said earlier...

I used the incorrect wording in my original post and have edited it. My bolt never closed on the no-go gauge with or without the extractor

 

[Howa4AU]

Grease up the bolt and start firing it- maybe with a string around the trigger for the first few shots

 

[LoneWolfUSMC]

I used the incorrect wording in my original post and have edited it. My bolt never closed on the no-go gauge with or without the extractor

Then your rifle is fine. Go shoot it.

To get an exact measurement you need to remove the ejector AND extractor. I will sometimes fudge it if I am trying to save time, but if I have any question I go back and remove the extractor and ejector and check it again.

 

[problemchild]

If anything goes horribly wrong I call first dibs on his left over ammo.

 

[cjlane]

If anything goes horribly wrong I call first dibs on his left over ammo.

hahahaha now you are at the back of the line