?? Headspace adjust - AR ??

[palmtree]

I understand headspace adjustment on an AK. I dont see how its done on a AR, and havent seen anyhting on youtube for it. Seems everyone is selling BCG's seperately, and they say to check headspace. How does adjustment work?
The only thing I can think of is shlmming barrel to front of receiver, or a series of different barrel extensions, that extend diff lengths. thanks

[nate76239]

https://gundigest.com/article/what-is-headspace-and-why-does-it-matter

[sigstroker]

Assuming everything is made to spec, usually it's just a stackup of tolerances, aka bad luck, if your headspace is off. Try a different bolt. It's easier than trying a different barrel.

[palmtree]

I got it, chances are buying an extra bcg, its gonna work. thanks, and thank you for the article link, I like links like that

[ar15barrels]

I understand headspace adjustment on an AK. I dont see how its done on a AR, and havent seen anyhting on youtube for it. Seems everyone is selling BCG's seperately, and they say to check headspace. How does adjustment work?
The only thing I can think of is shlmming barrel to front of receiver, or a series of different barrel extensions, that extend diff lengths. thanks

The AR design does not allow for headspace adjustment.
When parts are in-spec, a rifle should pass gauging.
The military armorer manual says that you first replace the bolt and if that does not solve the problem, then you replace the barrel.
Shimming the barrel forward in the receiver does nothing as the locking lugs and the bolt carrier group simply move forward with the barrel extension.

Having said that, it is sometimes possible to adjust the headspace, but it does require machining of the barrel and that is dependent on an absence of chrome lining or any hard surface treatment.
What you have to do is remove the barrel extension and either ream the chamber deeper if the headspace is short or face off the back of the barrel if the headspace is long.
Doing this causes an alignment problem with the gas port, front sight base and any markings on the barrel so you then have to drill a new gas port and re-drill for front sight base and simply deal with the markings being off of alignment.
No manufacturer does this work because it's more labor cost to the manufacturer than simply replacing the barrel with a new one.

I do this kind of work.

[palmtree]

Thank you for the extra explanation. I should have known, that shimming the barrel wouldnt make a difference. While were on this subject, I'm curious to why some well known manufacture3ses, such as Midwest Industries, sell a almost complete upper, but BCG, isnt included? I tend not to think its to save money, they cant be fooling anybody. Maybe liability loopholes? Id think manufactured test fired complete uppers would be favored. thanks

[sigstroker]

When Bushmaster was still around, that was their claim to fame. They sold complete uppers with bcg that were headspaced and test fired.

[ar15barrels]

I'm curious to why some well known manufacture3ses, such as Midwest Industries, sell a almost complete upper, but BCG, isnt included? I tend not to think its to save money, they cant be fooling anybody. Maybe liability loopholes?

I don't know if it's related to Federal Excise Tax, but a court did opine a couple years ago that the AR upper receiver should be considered the firearm instead of the AR lower receiver.

If this were taken to be true, then a complete AR upper receiver assembly with a bolt carrier and charging handle could be subjected to Federal Excise Tax.

If you sell a $1000 firearm, you pay $110 in tax.
You can reduce your federal excise tax burden by selling firearms in parts that are not fully assembled.
Then the tax is only due on the firearms receiver.

An example of how to reduce your federal excise tax burden is that you sell a $100 receiver, and you pay $11 in tax and then you sell a $900 parts kit separately and let the end user assemble the gun.
The receiver and the parts kit have to ship in separate shipments and not appear on a single invoice.

[palmtree]

thanks for the info