Concerned about building one myself from different barrel and upper manufacturers.
Since it's not talked about in any info I can find (after much looking) , I'm assuming headspace is not adjustable in the barrel to upper attachment process... just crank it down and get what you get. Throw in the go/no go gauges and forget the precision because it's an auto loader after all? Not finding comprehensive info anywhere. Even a major barrel maker offers to build me a chambered / headspaced barrel, which by definition, is impossible not having the bolt.        

Head space is in the barrel extension and it’s done when the barrel was made. You really don’t need to worry about it unless you’re using used parts. Good idea to have it checked anyways if you’re unsure.

no control over it other than using a new good quality bolt

It is possible to change the headspacing on the barrel, but that would require using a different barrel extension.  To get one that headspaces properly yet lines up perfectly can be incredibly difficult.  The only practical thing you can do to change it is try different bolts.  If the barrel is headspaced properly (which it should be if tested at the factory and it should be), and the bolt isn't improperly manufactured and doesn't have undue wear, chances are 99.999%+ that the headspace will be just fine.

Matched bolts to premium barrels is just someone going through a bag of bolts trying to find the one that allows for the minimum headspace to that particular extension.

In all likelyhood, you will not need to worry about headspace nor test it.  I've built AR's and tested those and every AR/M16 upper I have with all my bolts and none have ever been out of tolerance.

Quoted: It is possible to change the headspacing on the barrel, but that would require using a different barrel extension.  To get one that headspaces properly yet lines up perfectly can be incredibly difficult.  The only practical thing you can do to change it is try different bolts.  If the barrel is headspaced properly (which it should be if tested at the factory and it should be), and the bolt isn't improperly manufactured and doesn't have undue wear, chances are 99.999%+ that the headspace will be just fine. Matched bolts to premium barrels is just someone going through a bag of bolts trying to find the one that allows for the minimum headspace to that particular extension. In all likelyhood, you will not need to worry about headspace nor test it.  I've built AR's and tested those and every AR/M16 upper I have with all my bolts and none have ever been out of tolerance.

What is in red is not correct, no need to exchange.

Quoted: Quoted: It is possible to change the headspacing on the barrel, but that would require using a different barrel extension.  To get one that headspaces properly yet lines up perfectly can be incredibly difficult.  The only practical thing you can do to change it is try different bolts.  If the barrel is headspaced properly (which it should be if tested at the factory and it should be), and the bolt isn't improperly manufactured and doesn't have undue wear, chances are 99.999%+ that the headspace will be just fine. Matched bolts to premium barrels is just someone going through a bag of bolts trying to find the one that allows for the minimum headspace to that particular extension. In all likelyhood, you will not need to worry about headspace nor test it.  I've built AR's and tested those and every AR/M16 upper I have with all my bolts and none have ever been out of tolerance. What is in red is not correct, no need to exchange.

It is you that is incorrect, the statement is absolutely true.  I didn't say you need to exchange, all I said was that it was possible as that is how headspacing is set on the barrel at the factory or otherwise.  I continued to say that it is impractical and unnecessary.  If you need to change headspacing, change bolts.  He didn't ask if he needed to change headspace, he asked if one can change the headspace on a barrel, which one can, if they change the barrel extension.

To leftyshooter, the factory can set correct headspace because there is a defined specification for it in the barrel assembly.  If the bolt is also in spec then proper headspacing will be achieved.  If either the bolt or barrel is improperly headspaced, then the headspace will be incorrect.  The manufacturer does their part to set the headspace on the barrel properly, and the bolt manufacturer does their part to make the bolt to specs that will achieve proper headspace with an in spec barrel assy.  You shouldn't have to do anything but drop in a good bolt.

Good information, I've learned a lot. Thanks.

In a very general sense this information is good however headspace can be adjusted by a gunsmith with machinist skills by removing the barrel extention and cutting the shoulder back allowing the extention to be screwed on farther. This is rather advanced gunsmithing but is fairly simple to some of the old pros out there. This may also involve realligning the sights and indexing pin. Some may choose to modify the extension itself in order to work on the cheaper part. less risk of damage.  A good gunsmith can get you a perfect headspace if you really want to pay .
with todays manufacturing methods it is possible to get two parts from different manufacturers that are compatable one of the beuatys of the AR-15 is the interchangability. As far as headspacing using a bag of bolts I seirousley doubt that. More realisticaly if it dosent headspace propperley at the factory it probably gets checked for specs and either scrapped or sent back through the supply system to be corrected. Do you really think they are willing to pay a guy to rummage through all of the bolts in stock in order to get good headspace one one barrel that is probably + or - the correct tollerance and is junk any how. How long would that take and how much dose he get paid per. hour ?  Now who is doing his job inspecting the rifles he should be checking while he is dicking aound trying to find one bolt that will make this rifle headspace right. I really dont think so.

As far as headspacing using a bag of bolts I seirousley doubt that.

He didn't say that they used a bag of bolts until they get proper headspace, he said that it's to find optimal headspace, like .002" over a go gauge, etc.

Now, if they even do that it would surprise the hell out of me. Usually the bolt is sold with it to ensure that they are good to go-as opposed to trying an unknown bolt and having to check headspace-which can be a problem if you don't have the gauges.

Quoted: Quoted: Quoted: It is possible to change the headspacing on the barrel, but that would require using a different barrel extension.  To get one that headspaces properly yet lines up perfectly can be incredibly difficult.  The only practical thing you can do to change it is try different bolts.  If the barrel is headspaced properly (which it should be if tested at the factory and it should be), and the bolt isn't improperly manufactured and doesn't have undue wear, chances are 99.999%+ that the headspace will be just fine. Matched bolts to premium barrels is just someone going through a bag of bolts trying to find the one that allows for the minimum headspace to that particular extension. In all likelyhood, you will not need to worry about headspace nor test it.  I've built AR's and tested those and every AR/M16 upper I have with all my bolts and none have ever been out of tolerance. What is in red is not correct, no need to exchange. It is you that is incorrect, the statement is absolutely true.  I didn't say you need to exchange, all I said was that it was possible as that is how headspacing is set on the barrel at the factory or otherwise.  I continued to say that it is impractical and unnecessary.  If you need to change headspacing, change bolts.  He didn't ask if he needed to change headspace, he asked if one can change the headspace on a barrel, which one can, if they change the barrel extension. To leftyshooter, the factory can set correct headspace because there is a defined specification for it in the barrel assembly.  If the bolt is also in spec then proper headspacing will be achieved.  If either the bolt or barrel is improperly headspaced, then the headspace will be incorrect.  The manufacturer does their part to set the headspace on the barrel properly, and the bolt manufacturer does their part to make the bolt to specs that will achieve proper headspace with an in spec barrel assy.  You shouldn't have to do anything but drop in a good bolt.

No gunsmith worth the salt would ever exchange bolts to headspace an AR barrel, that is the most ridiculous internet myth I have ever read on here and it is totally false.

You cut the chamber to the bolt, not exchange the bolt to the chamber.

Free bore for SAMMI spec .223 is 40-60 thousandths, good luck on finding a serviceable bolt that has that much slack.

Total cost for a gunsmith to ream a chamber to increase headspace in a non-chrome lined barrel should run you around 65.00-85.00, further more if anyone tells you to exchange a barrel extension on a chrome lined chamber and barrel they do not have a clue on how to do it.

I have over 500 AR barrels from scratch under my belt, not many but around 500 more than you.

It is not that uncommon to have to swap bolts to get a go gage to close on some new barrels. I have had to do it a few times. Bolts do vary.

Quoted: Quoted: Quoted: Quoted: It is possible to change the headspacing on the barrel, but that would require using a different barrel extension.  To get one that headspaces properly yet lines up perfectly can be incredibly difficult.  The only practical thing you can do to change it is try different bolts.  If the barrel is headspaced properly (which it should be if tested at the factory and it should be), and the bolt isn't improperly manufactured and doesn't have undue wear, chances are 99.999%+ that the headspace will be just fine. Matched bolts to premium barrels is just someone going through a bag of bolts trying to find the one that allows for the minimum headspace to that particular extension. In all likelyhood, you will not need to worry about headspace nor test it.  I've built AR's and tested those and every AR/M16 upper I have with all my bolts and none have ever been out of tolerance. What is in red is not correct, no need to exchange. It is you that is incorrect, the statement is absolutely true.  I didn't say you need to exchange, all I said was that it was possible as that is how headspacing is set on the barrel at the factory or otherwise.  I continued to say that it is impractical and unnecessary.  If you need to change headspacing, change bolts.  He didn't ask if he needed to change headspace, he asked if one can change the headspace on a barrel, which one can, if they change the barrel extension. To leftyshooter, the factory can set correct headspace because there is a defined specification for it in the barrel assembly.  If the bolt is also in spec then proper headspacing will be achieved.  If either the bolt or barrel is improperly headspaced, then the headspace will be incorrect.  The manufacturer does their part to set the headspace on the barrel properly, and the bolt manufacturer does their part to make the bolt to specs that will achieve proper headspace with an in spec barrel assy.  You shouldn't have to do anything but drop in a good bolt. No gunsmith worth the salt would ever exchange bolts to headspace an AR barrel, that is the most ridiculous internet myth I have ever read on here and it is totally false. You cut the chamber to the bolt, not exchange the bolt to the chamber. Free bore for SAMMI spec .223 is 40-60 thousandths, good luck on finding a serviceable bolt that has that much slack. Total cost for a gunsmith to ream a chamber to increase headspace in a non-chrome lined barrel should run you around 65.00-85.00, further more if anyone tells you to exchange a barrel extension on a chrome lined chamber and barrel they do not have a clue on how to do it. I have over 500 AR barrels from scratch under my belt, not many but around 500 more than you.

You are again incorrect.  I didn't say you change bolts to change headspacing on the barrel, I said you change the barrel extension to change the headspace on a barrel.  You change the bolt to change the final headspace with a particular barrel assy.  Are you dyslexic?  You are mixing my statements up. This is not a myth, this is how it's done.  Next bust - you can buy barrel extensions in the white and have them chromed if you like, try Brownells pn 231-015-032.  However, the chance of buying one that will headspace correctly out of the box yet line up with the index pin is very, very slim though I do know someone who lucked into it, twice.  10 barrel extensions and you would be lucky that one lined up properly.  However for those that want to machine the extension the part is available.  I think you are just confusing what I am actually writing.

About the "bag" of bolts.  I just meant a selection of bolts.  This is how CLE does it.  This is how they produced a matched bolt for my military SPR barrel as Lawman said, they go through and pick out a bolt that produces the optimal minimum headspace with a particular barrel assembly BECAUSE THE HEADSPACE IS ALREADY SET ON THE BARREL AT THE FACTORY VIA THE BARREL EXTENSION!  CAN YOU ASSIMILATE THIS?  YOU ARE CONTROLLING HEADSPACE VIA THE BOLT INSTEAD OF THE EXTENSION AS ONE IS PRACTICAL AND THE OTHER IS NOT!  CHANGING EITHER WILL CHANGE THE HEADSPACE! How can you assemble that many uppers and not understand this?  I have only built a few but it doesn't take a smith to comprehend what I am writing.

ETA:  Just to be 110% clear, when I say barrel assy, I am referring to a barrel with barrel extension and index pin.  When I say barrel I mean just the barrel.  When I say properly headspaced, I am referring to the final headspace distance determined by the bolt and barrel extension (thus chamber) TOGETHER.  Either can be shorter or longer and still be properly headspaced if the other part is likewise longer or shorter (or use the terms tighter and looser, whatever you prefer).  It is far easier to CONTROL final headspace by using bolts than it is to reset the headspace on the barrel assembly by altering or replacing the barrel extension.  EASIER, NOT IMPOSSIBLE.  There are specs for both barrel extension/chamber and bolt that TOGETHER will determine final headspace.

tag

w00t w00t w00t!!!

Quoted: Quoted: Quoted: Quoted: Quoted: It is possible to change the headspacing on the barrel, but that would require using a different barrel extension.  To get one that headspaces properly yet lines up perfectly can be incredibly difficult.  The only practical thing you can do to change it is try different bolts.  If the barrel is headspaced properly (which it should be if tested at the factory and it should be), and the bolt isn't improperly manufactured and doesn't have undue wear, chances are 99.999%+ that the headspace will be just fine. Matched bolts to premium barrels is just someone going through a bag of bolts trying to find the one that allows for the minimum headspace to that particular extension. In all likelyhood, you will not need to worry about headspace nor test it.  I've built AR's and tested those and every AR/M16 upper I have with all my bolts and none have ever been out of tolerance. What is in red is not correct, no need to exchange. It is you that is incorrect, the statement is absolutely true.  I didn't say you need to exchange, all I said was that it was possible as that is how headspacing is set on the barrel at the factory or otherwise.  I continued to say that it is impractical and unnecessary.  If you need to change headspacing, change bolts.  He didn't ask if he needed to change headspace, he asked if one can change the headspace on a barrel, which one can, if they change the barrel extension. To leftyshooter, the factory can set correct headspace because there is a defined specification for it in the barrel assembly.  If the bolt is also in spec then proper headspacing will be achieved.  If either the bolt or barrel is improperly headspaced, then the headspace will be incorrect.  The manufacturer does their part to set the headspace on the barrel properly, and the bolt manufacturer does their part to make the bolt to specs that will achieve proper headspace with an in spec barrel assy.  You shouldn't have to do anything but drop in a good bolt. No gunsmith worth the salt would ever exchange bolts to headspace an AR barrel, that is the most ridiculous internet myth I have ever read on here and it is totally false. You cut the chamber to the bolt, not exchange the bolt to the chamber. Free bore for SAMMI spec .223 is 40-60 thousandths, good luck on finding a serviceable bolt that has that much slack. Total cost for a gunsmith to ream a chamber to increase headspace in a non-chrome lined barrel should run you around 65.00-85.00, further more if anyone tells you to exchange a barrel extension on a chrome lined chamber and barrel they do not have a clue on how to do it. I have over 500 AR barrels from scratch under my belt, not many but around 500 more than you. You are again incorrect.  I didn't say you change bolts to change headspacing on the barrel, I said you change the barrel extension to change the headspace on a barrel.  You change the bolt to change the final headspace with a particular barrel assy.  Are you dyslexic?  You are mixing my statements up. This is not a myth, this is how it's done.  Next bust - you can buy barrel extensions in the white and have them chromed if you like, try Brownells pn 231-015-032.  However, the chance of buying one that will headspace correctly out of the box yet line up with the index pin is very, very slim though I do know someone who lucked into it, twice.  10 barrel extensions and you would be lucky that one lined up properly.  However for those that want to machine the extension the part is available.  I think you are just confusing what I am actually writing. About the "bag" of bolts.  I just meant a selection of bolts.  This is how CLE does it.  This is how they produced a matched bolt for my military SPR barrel as Lawman said, they go through and pick out a bolt that produces the optimal minimum headspace with a particular barrel assembly BECAUSE THE HEADSPACE IS ALREADY SET ON THE BARREL AT THE FACTORY VIA THE BARREL EXTENSION!  CAN YOU ASSIMILATE THIS?  YOU ARE CONTROLLING HEADSPACE VIA THE BOLT INSTEAD OF THE EXTENSION AS ONE IS PRACTICAL AND THE OTHER IS NOT!  CHANGING EITHER WILL CHANGE THE HEADSPACE! How can you assemble that many uppers and not understand this?  I have only built a few but it doesn't take a smith to comprehend what I am writing. ETA:  Just to be 110% clear, when I say barrel assy, I am referring to a barrel with barrel extension and index pin.  When I say barrel I mean just the barrel.  When I say properly headspaced, I am referring to the final headspace distance determined by the bolt and barrel extension (thus chamber) TOGETHER.  Either can be shorter or longer and still be properly headspaced if the other part is likewise longer or shorter (or use the terms tighter and looser, whatever you prefer).  It is far easier to CONTROL final headspace by using bolts than it is to reset the headspace on the barrel assembly by altering or replacing the barrel extension.  EASIER, NOT IMPOSSIBLE.  There are specs for both barrel extension/chamber and bolt that TOGETHER will determine final headspace.

Best line of shade tree gunsmithing tech school education I have read in long time.

First of all you do not know what you are talking about, you can come down here to Virginia and we can show you how it is done properly.

I have a barrel extension socket in the shop and do not need to do all the Vodoo that you suggest, do I need to make a video and show you how it is done?

Yes, you do, you can show the rest of the real world because you don't seem to live in it.  You really don't know what your talking about, do you?  When you pull your head out and get a fresh breath of air, come on up here and I'll give you a visual aid since you can't seem to understand it in writing.  Until then I am done with you, you are a lost cause.

leftyshooter, sorry I wasted so much of your thread trying to educate the goofball.  Again, put your upper together, the barrel is headspaced at the factory and you won't be changing it.  Drop in a good bolt, check it with headspace gauges if you want to be sure it's okay, and bang away.  In all likely case it will headspace just fine.

If you need further instruction, read the tacted thread which repeats what I have been saying.  Long-Rifle I suggest you do the same and learn how the rest of the world does it.  Take your time with the big words.

Assembling your own AR

Q3. What about checking the headspace after I assemble? A3. While checking your headspace is never a bad idea, it isn't required for this operation. The headspace of an AR is set by the bolt's fit into the barrel extension. As long as you are using a good quality bolt and barrel, that was headspaced by the manufacturer, you are good to go. If you are assembling very old/used barrel/bolt, then you might want to consider checking headspace. Changing the barrel has no bearing on headspace, because the barrel's seating in the upper receiver makes no difference, it is all in the bolt and barrel extension.

Get em Mike! You'd better watch out though, else they'll realize we're not just a bunch of ingrown hicks up here.

I thought he was serious but I think he was just trying to get my goat.  I realize now he is just a troll, I'm not used to having to deal with them, most people I deal with are serious and have a clue.

At least people like MarkM are funny, this one is just an idiot.

Quoted: I thought he was serious but I think he was just trying to get my goat.  I realize now he is just a troll, I'm not used to having to deal with them, most people I deal with are serious and have a clue. At least people like MarkM are funny, this one is just an idiot.

long-rifle-tactical has a mobile work bench and vise that he puts on his truck hitch at the VA arfcom blasts to work on all our stuff....i've seen him barrel an upper in the range parking lot!! this man forgets more stuff than you will ever hope to learn

He did it again, made an irrelevant comment.  So it's a picture of a barrel extension wrench.  What is the point?  If you need the wrench to take the extension off, that is what you use if need be though some people have used a converted broken bolt (not recommended).  There is no point even being made but then everything he says has nothing to do with what I have said.  If he only had a clue.

It's obvious he knows things but everything I have said is true.  He simply mixes up what I am saying and he makes irrelevant posts.  I work on gear a the range at Alaska shoots, so what?  I have a barrel extension wrench as well (never needed it though), so what?  I never said you couldn't remove one, never said you couldn't work on one.  I pointed out the part if you want to get one and work on it and Brownells also carries the wrench.  You can plate the extension in chrome if you want (allowing for thickness).  I also said you can work on them.  About the only thing I said about extensions is that they, along with the bolt, determine final headspace - absolutely true.  It's also absolutely true that a barrel extension picked randomly will most likely not line index properly to the desired headspace on the barrel.  So what, some work must be done to it to correct, that's a given, that's how it is done.  What is the big mystery?  I have a full machine shop with a C2 and have done the work myself. BFD.  To repeat, I said it is simply impractical for the average end user, not impossible.

Point out something that I said is incorrect.  It's hard to debate someone who makes no relevant posts no matter what his skills are.  The skill he is lacking is relevant posting.  He may be have uber skills but he posts out of his ass, generalizing, and mixing statements.

Quoted: long-rifle-tactical has a mobile work bench and vise that he puts on his truck hitch at the VA arfcom blasts to work on all our stuff....i've seen him barrel an upper in the range parking lot!!

I have a portable vise and a nice armorer's kit -- and I can barrel an upper in the bathroom if you want me to.

Quoted: I have a portable vise and a nice armorer's kit -- and I can barrel an upper in the bathroom if you want me to.

Good MarkM impression, LOL.  Personally I was going to say phone booth while taking a call.  All I need is my AR tools kit and portable vice.  For milling and finishing I need my shop though.

Quoted: Quoted: long-rifle-tactical has a mobile work bench and vise that he puts on his truck hitch at the VA arfcom blasts to work on all our stuff....i've seen him barrel an upper in the range parking lot!! I have a portable vise and a nice armorer's kit -- and I can barrel an upper in the bathroom if you want me to.

I could chamber a M1A and a AR15 in my bathroom as well, does that make me uber tactical?

Quoted: I could chamber a M1A and a AR15 in my bathroom as well, does that make me uber tactical?

More uber tactical than me, as I don't do chamber work.

i'm lost.  is this a chicken or the egg debate?  which one of you gets the BS award?

Quoted: i'm lost.  is this a chicken or the egg debate?  which one of you gets the BS award?

In preparation, some of us work for a living.

Thanks Tweak, far more eloquent for what I was trying to say.  While a smith can make adjustments to a barrel assy, it's impractical to the average end user with no tools or equipment and even then timing becomes an issue with resetting the extension if you can't ream the chamber if it's chromed since you don't want to ruin the plating.  I have also found it's difficult to "luck" into a replacement extension that will properly line up though I knew someone who did it twice within 10 tries.  It's easier to swap bolts (for the non-smith) as long as you only need to adjust small amount.  Using the military 5.56 gauge one can see that it would have to be a really, really worn or badly made to be out.  Not being a big armorer, I haven't found or built an upper that wouldn't pass the military 5.56 gauge with the given bolt and barrel assy.

Edited to add, the military 5.56 gauge (at least the ones I use) are cut for the ejector unlike my civvie gauges for which I remove the ejector before use.

Quoted: Quoted: Edited to add, the military 5.56 gauge (at least the ones I use) are cut for the ejector unlike my civvie gauges for which I remove the ejector before use. that's the FIELD gage right?

Yes sorry, I was referring specificly to the Colt M16 Field NSN gauge.  I use custom civvie gauges made for a full range but at informal MG shoots I usually just bring the Field gauge cause it's handy.

Tweak:

Do you ever use a Firing Pin Protrusion Gauge swapping the bolt?

If we did depot level maintenance it was required.

(1) Buy a good quality barrel assembly.

(2) Buy a good quality bolt.

(3) Assemble.

(4) Go shooting.

Quoted: Quoted: Yes sorry, I was referring specificly to the Colt M16 Field NSN gauge. . just checking bc the mil GO and NOGO aren't cut for the extractor or ejector, they look just like Forster gages just different dimensions.

Yes, that is the case.  I bring the Field gauge so I don't have to whip out my ejector extraction vice tool (which just makes it easier).  I've never noticed any others that are cut for the ejector.  Something else to note, I find the standard civvie go/no-go gauges, depending on brand, vary in dimension.

A_Free_Man:  Short and sweet, excellent

Quoted: Quoted: Yes sorry, I was referring specificly to the Colt M16 Field NSN gauge. . just checking bc the mil GO and NOGO aren't cut for the extractor or ejector, they look just like Forster gages just different dimensions. LRT, I have a FP gage but only use it occassionaly when there is a question about it. The problems I see more often are firing pin holes in the bolts being off center.

Good point in blue!


The firing pin issue is a good point where as it may hang or drag increasing lock time and misfires if not centered, I have also witnessed bolt carriers have minor machine chatter inside the carrier were it would not allow the firing pin to set forward.

This was a out of a bag bolt carrier, I attempt to impress  purchasing parts from reputable vendors who stand behind what they sell rather than what someone can buy on the cheap.