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-   -   AR Headspacing (http://www.firearmstalk.com/forums/f33/ar-headspacing-91152/)

triggerjob 05-23-2013 06:04 PM

AR Headspacing
 
Is there any reason why a person shouldn't measure AR headspace with the barrel out of the upper?

LIke you wanna know its right before you assemble and torque stuff down.

robocop10mm 05-24-2013 05:34 AM

Headspace is set and not really adjustable. If you have properly made, in spec components, you should not have an issue

JonM 05-24-2013 11:30 AM

All you really need for an ar15 is a field gage. To measure headspace on a ar15 you need to remove the ejector which protrudes through the bolt face the drop the field gage into the chamber if the bolt closes your barrel needs to be replaced. There is no removing the extension milling the chamber end down then reinstallijg the extension like you can do with other firearms.

Ar15 barrels are meant to be tossed and replaced once they exceed max headspacing.

70cuda383 05-24-2013 11:43 AM

Quote:

Originally Posted by JonM (Post 1256705)
All you really need for an ar15 is a field gage. To measure headspace on a ar15 you need to remove the ejector which protrudes through the bolt face the drop the field gage into the chamber if the bolt closes your barrel needs to be replaced. There is no removing the extension milling the chamber end down then reinstallijg the extension like you can do with other firearms.

Ar15 barrels are meant to be tossed and replaced once they exceed max headspacing.


so head spacing changes?! I thought it was set on manufacturing/assembly and it was good to go.

so, now one needs to check it over the life of the barrel? how many rounds does it typically take for the head space to open up?

triggerjob 05-24-2013 01:48 PM

Generally the headspace won't open up, unless you've shot out the chamber.

But it could be wrong from the factory. If you have an AR don't worry about it unless you are having issues with bulged or ringed cases.

I'm aksing more along the lines of a wonky technical question.

Yes head space can be adjusted on an AR but nobody does it cause the barrels are generally cheap enough it ain't worth doin, if its right from the factory its not going to open up unless the chamber is shot out or your bolt is worn.

JonM 05-25-2013 12:51 PM

All rifles increase in headspace as they are used. Typical service life of a ar15 barrel is 20000 to 40000 rounds. There is a gap because of different barrel materials. A higher quality military grade machine gun barrel will last much longer than your typical stainless steel barrel you find on most cheaper budget ar15.

Service life is how long until the gun is not safe to shoot.

Competition shooters replace barrels much sooner since accuracy degrades greatly long before you hit the point a ar15 will close on a field gage

Once you hit the 10000 round mark i would start checking it everytime you service the rifle.

gunnut07 05-26-2013 01:03 AM

Your throat will shoot out before having head space problems depending on how you shoot. If you do a lot of rapid fire with a hot gun throat erosion will increase.


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