First AR build/headspace

savagetroll · April 25, 2016, 09:06 PM

I am in the process of building my first AR15. Going with a Daniel Defense CHF barrel and Daniel Defense bolt. My question is, is it necessary to check headspace, and if so what is the best way to do so? thanks for any input

burrhead · April 26, 2016, 12:00 AM

I've built three ARs and never checked the headspace but it's not a bad idea. If you want to check, get a no-go and field headspace gauge.

http://www.brownells.com/.aspx/lid=1...se-Them-Part-I

Chainsaw. · April 26, 2016, 08:09 AM

Yup, built two, didnt check head space, I did how ever use a dummy round to make sure the bolt was locking and unlocking without issue.

FrankenMauser · April 26, 2016, 08:11 AM

Check headspace before installing the barrel.

Strip the bolt.
Clean the gauge, bolt, barrel, barrel extension, and locking lugs.
Insert the gauge, and see if the bolt will lock. (Free-spinning in the barrel extension is fine when using a "go" gauge.)

I've built half a dozen, or more.
Most had no issues with headspace (and weren't checked with actual gauges - at least initially).
But the one that did have bad headspace... I could have saved myself innumerable headaches by checking headspace before installing the barrel, rather than after running into chambering issues.

Mobuck · April 26, 2016, 10:38 AM

The only AR headspace problem I've found was on a 5.45x39. I think the barrel/extension had been headspaced with a 7,62x39 bolt or something stranger yet?? First round separated the steel case leaving the shoulder and neck in the chamber.
I have found a couple of .223/5.56 chambers that were too tight with certain bolts requiring a little trial and error fitting with different bolts. I don't swap bolts after more than a few test rounds unless there's a specific problem. The way I see it: new bolt-new chamber= no problem, new bolt-relatively low round chamber=likely no problem, high round used bolt-any chamber other than the one it came from=expect a problem.

savagetroll · April 26, 2016, 10:46 AM

Thanks for all of the advice. New quality barrel and bcg, but never hurts to be sure.

tobnpr · April 26, 2016, 06:40 PM

You really shouldn't need to as long as the barrel was chambered correctly and the extension is in spec..and with both barrel and bolt by Daniel Defense it's VERY unlikely you're going to find an issue. No more likely, IMO, than an 700 rolling off the line at Remington with excessive headspace.

You could always take an inert round, or case, confirm the bolt rotates fully into battery easily, and use a couple layers of cellophane packing tape (if you have a mike to measure the thickness of it) added to the case head to approximate a no-go gauge.

If you buy a gauge, no-go is what you want...no need for a field gauge. If it closes on a no-go you need take it no further on a new rifle.

It would be interesting to know if D.D. actually verifies headspace on assembled uppers or rifles as part of QC, or if they just assemble the components.

ms6852 · April 26, 2016, 07:16 PM

When talking about headspace on an AR type rifle is like asking the proverbial question: What came first, the chicken or the egg. You will find 1000 people that say headspace is not necessary, and you will find 1000 that say it is necessary. As mentioned above if you do decide, using a GO, NOGO gauge will suffice. If you decide not to headspace, that too will be find.

Mobuck · April 27, 2016, 07:10 AM

Theoretically, the chamber was cut to dimension using a "bench bolt" which to me indicates a test bolt gauged to be within specifications for the design. I don't know the tolerances allowed for bolts or barrel extensions but there's always a possibility of ending up with marginally long or short headspace due to tolerance stacking.
I keep a handful of inert cartridges for testing function of new AR assemblies. I also have a "test only" firing pin(tip ground off to prevent ANY chance of AD) that I can use with live ammo for function testing. I often use this to check fit of reloads on one of my tight chambered AR's to make sure they fully chamber.

April 25, 2016, 09:06 PM	#1
savagetroll Member Join Date: January 16, 2016 Posts: 20	First AR build/headspace I am in the process of building my first AR15. Going with a Daniel Defense CHF barrel and Daniel Defense bolt. My question is, is it necessary to check headspace, and if so what is the best way to do so? thanks for any input

April 26, 2016, 12:00 AM	#2
burrhead Senior Member Join Date: July 6, 1999 Location: Chihuahuan desert, Texas Posts: 1,148	I've built three ARs and never checked the headspace but it's not a bad idea. If you want to check, get a no-go and field headspace gauge. http://www.brownells.com/.aspx/lid=1...se-Them-Part-I __________________ Join the GOA, SAF and the TSRA I'm offended by people that are easily offended.

April 26, 2016, 08:11 AM	#4
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	Check headspace before installing the barrel. Strip the bolt. Clean the gauge, bolt, barrel, barrel extension, and locking lugs. Insert the gauge, and see if the bolt will lock. (Free-spinning in the barrel extension is fine when using a "go" gauge.) I've built half a dozen, or more. Most had no issues with headspace (and weren't checked with actual gauges - at least initially). But the one that did have bad headspace... I could have saved myself innumerable headaches by checking headspace before installing the barrel, rather than after running into chambering issues. __________________ Don't even try it. It's even worse than the internet would lead you to believe.

April 26, 2016, 06:40 PM	#7
tobnpr Senior Member Join Date: August 1, 2010 Location: Tampa Bay Posts: 4,556	You really shouldn't need to as long as the barrel was chambered correctly and the extension is in spec..and with both barrel and bolt by Daniel Defense it's VERY unlikely you're going to find an issue. No more likely, IMO, than an 700 rolling off the line at Remington with excessive headspace. You could always take an inert round, or case, confirm the bolt rotates fully into battery easily, and use a couple layers of cellophane packing tape (if you have a mike to measure the thickness of it) added to the case head to approximate a no-go gauge. If you buy a gauge, no-go is what you want...no need for a field gauge. If it closes on a no-go you need take it no further on a new rifle. It would be interesting to know if D.D. actually verifies headspace on assembled uppers or rifles as part of QC, or if they just assemble the components. __________________ Remington 700/Savage Rebarreling /Action Blueprinting 07 FFL /Mosin-Nagant Custom Shop/Bent Bolts Genuine Cerakote Applicator www.biggorillagunworks.com

April 26, 2016, 07:16 PM	#8
ms6852 Senior Member Join Date: April 3, 2010 Location: Texas Posts: 1,394	When talking about headspace on an AR type rifle is like asking the proverbial question: What came first, the chicken or the egg. You will find 1000 people that say headspace is not necessary, and you will find 1000 that say it is necessary. As mentioned above if you do decide, using a GO, NOGO gauge will suffice. If you decide not to headspace, that too will be find. __________________ ONLY TWO DEFINING FORCES HAVE GIVEN UP THEIR LIVES FOR YOU. ONE IS JESUS CHRIST FOR YOUR SOUL AND THE OTHER IS THE AMERICAN SOLDIER FOR YOUR FREEDOM.

April 26, 2016, 08:09 AM	#3
Chainsaw. Senior Member Join Date: September 12, 2015 Location: Issaquah WA. Its a dry rain. Posts: 1,774	Yup, built two, didnt check head space, I did how ever use a dummy round to make sure the bolt was locking and unlocking without issue.

April 26, 2016, 10:38 AM	#5
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	The only AR headspace problem I've found was on a 5.45x39. I think the barrel/extension had been headspaced with a 7,62x39 bolt or something stranger yet?? First round separated the steel case leaving the shoulder and neck in the chamber. I have found a couple of .223/5.56 chambers that were too tight with certain bolts requiring a little trial and error fitting with different bolts. I don't swap bolts after more than a few test rounds unless there's a specific problem. The way I see it: new bolt-new chamber= no problem, new bolt-relatively low round chamber=likely no problem, high round used bolt-any chamber other than the one it came from=expect a problem.

April 26, 2016, 10:46 AM	#6
savagetroll Member Join Date: January 16, 2016 Posts: 20	Thanks for all of the advice. New quality barrel and bcg, but never hurts to be sure.

April 27, 2016, 07:10 AM	#9
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	Theoretically, the chamber was cut to dimension using a "bench bolt" which to me indicates a test bolt gauged to be within specifications for the design. I don't know the tolerances allowed for bolts or barrel extensions but there's always a possibility of ending up with marginally long or short headspace due to tolerance stacking. I keep a handful of inert cartridges for testing function of new AR assemblies. I also have a "test only" firing pin(tip ground off to prevent ANY chance of AD) that I can use with live ammo for function testing. I often use this to check fit of reloads on one of my tight chambered AR's to make sure they fully chamber.