Headspacing on 2 different AR barrels: need some input:

[BuildingConceptsllc]

So, I have 2 AR's with Bart barrels. They were chambered by 2 different smith's and have 2 different headspaces. They are .005" apart, one from the other. The shorter of the two chambers is in my "precision ar" and the longer is in more of an all around AR with a 1-10 razor on it. (1.464" ) & (1.469") is what the fires brass measures.

I am mainly shooting 77smk and 75bthp horn out of both and ideally the same exact load out of both. Still some shooting left to do to know if that's going to work well enough or not but it's looking promising now that i have the right powder charge and with a good bit of jump, shooting the 77smk which is a great thing.

So I'm wondering if that .005" is enough difference to matter in my accuracy and brass life (considering this brass is only used for AR's. I shoot lapua on all bolt guns.), and if so, should I pursue getting the shorter one, lengthened by .004"-.005" in order to make them the same? I'm pretty sure I can rent a reamer rig to do that by hand like I've done to the lands of other barrels but I'm not positive on that.

I wouldn't want to take a chance on messing up my CLE done barrel (which is the shorter chamber of the two). Both barrels have CLE chambers, but the shorter chambered one was done by CLE a few years back and the longer chambered one done by someone else recently. Why I didn't send a piece of fired brass with it, when it was done, I will never know. I just screwed that up so, now I'm trying to figure out if it's worth "fixing it" so to speak?

 

[jet_lagged]

Have you tried swapping a few bolts around to see if that would make the headspace closer together? Could be an easier option….

 

[BuildingConceptsllc]

Have you tried swapping a few bolts around to see if that would make the headspace closer together? Could be an easier option….

No I haven't because they are lefty so I don't even really try to mess with the bolts but now that you say that, with both being lefty I guess I could. One is a side charger with a piston kit but, the bolt itself should be swappable with another lefty bolt so, I will definitely see if that gets em close. They don't have to be exactly the same and really just a little closer and I wouldn't even worry about it. That's a good idea

 

[straightshooter1]

No I haven't because they are lefty so I don't even really try to mess with the bolts but now that you say that, with both being lefty I guess I could. One is a side charger with a piston kit but, the bolt itself should be swappable with another lefty bolt so, I will definitely see if that gets em close. They don't have to be exactly the same and really just a little closer and I wouldn't even worry about it. That's a good idea

Headspace involves two things:
How much the bolt face has been cut to spec.
How the chamber is cut at the shoulder datum.

It's not unusual for factory guns to have substantial difference in headspace. Though with modern CNC milling machines, tolerances tend to be much tighter these days. Swapping bolts is not a bad idea to see if they tighten up with the different chamber. Or, maybe instead of the bolts, the barrels can be swapped that might help???

If neither of these things help, just dedicate certain brass to each gun and size accordingly rather than using the same brass for both guns.

 

[BuildingConceptsllc]

Headspace involves two things:
How much the bolt face has been cut to spec.
How the chamber is cut at the shoulder datum.

It's not unusual for factory guns to have substantial difference in headspace. Though with modern CNC milling machines, tolerances tend to be much tighter these days. Swapping bolts is not a bad idea to see if they tighten up with the different chamber. Or, maybe instead of the bolts, the barrels can be swapped that might help???

If neither of these things help, just dedicate certain brass to each gun and size accordingly rather than using the same brass for both guns.

Yeah, why didn't I think of that????...............

 

[Rocketvapor]

Measure lug length and face depth of the bolts.
Difference is bolt's contribution to headspace.
If this is a 223 then the difference spec is 0.153" to 0.156", right or left hand.
HeadSpace is Chamber Depth including Extension, and Bolt.
You should be able to keep the brass separated by measuring as-fired dimensions.
Size some brass just to click in with both rifles, then measure.


Note that as-fired can be different just due to the action and gas.

 

[BuildingConceptsllc]

Measure lug length and face depth of the bolts.
Difference is bolt's contribution to headspace.
If this is a 223 then the difference spec is 0.153" to 0.156", right or left hand.
HeadSpace is Chamber Depth including Extension, and Bolt.
You should be able to keep the brass separated by measuring as-fired dimensions.
Size some brass just to click in with both rifles, then measure.


Note that as-fired can be different just due to the action and gas.

Good idea here as well. Thank you. I can measure the bolts and see if they will change the fired brass size, then if so, do it, and then test it.

Not sure what you mean about keeping the brass separate? I have the brass separated now and yes I can do that but I don't want to have to. At some point all of these different sized brass gets just too much, which is why I'd really like for these 2 AR's to be just the same , or close enough go the same where it won't effect my brass or accuracy to any significant amount.



Let's say the bolts do measure out differently and to my benefit, how much would I size down or what size would I then make my brass when I test it? ideally, swapping the two bolts would get the size difference down to .003" or less.

Yes its a 223, I should have included that in the OP.

 

[Snuby642]

(1.464" ) & (1.469") .

The 1.464 is what I consider standard. The 1.469 is what I consider shit.

I don't know if you can get a bolt to take up that slop?

We have 5 ar's within ( 0.0005 ) of each other ( 1.4640 - 1.4635 ) all I had to do was change 1 bcg.

I should contact whoever did the 1.469 work and ask if they could do something.

Sorting brass between 223's sucks.

 

[buyobuyo]

Since the shorter chamber is your "precision" gun, I wouldn't worry about it. Load for the shorter chambered gun and run it in both.

Also, do you mean 1.464 and 1.469 for the head space? 223 headspace is 1.4636 to 1.4736.

 

[Snuby642]

@buyobuyo

Good catch 1.4635 -1.4640

Old guy syndrome. Lol

That 1.469 is going to be plenty sloppy if you stick any box ammo in it.

I try to have 4 thousands or less in a gas gun, 3 - 3 1/2 is what I'm running.

I would take another thousands off but these days you never know when you range toy / hunting ar runs into an extended two way conflict.

 

[BuildingConceptsllc]

(1.464" ) & (1.469") .

The 1.464 is what I consider standard. The 1.469 is what I consider shit.

I don't know if you can get a bolt to take up that slop?

We have 5 ar's within ( 0.0005 ) of each other ( 1.4640 - 1.4635 ) all I had to do was change 1 bcg.

I should contact whoever did the 1.469 work and ask if they could do something.

Sorting brass between 223's sucks.

Yeah I wondered if that was kind of excessive. I may contact the Smith and see what he says.

I did swap the bolts and it did help. I'm now at

1.4655. With the shorter

1.4680 with the longer.

That's close enough to where I can probably load it for .0015" under the longer and be good but I'm still wondering if that's enough to effect my accuracy and/or brass life???? Thoughts by all ITT are welcome.

 

[BuildingConceptsllc]

Since the shorter chamber is your "precision" gun, I wouldn't worry about it. Load for the shorter chambered gun and run it in both.

Also, do you mean 1.464 and 1.469 for the head space? 223 headspace is 1.4636 to 1.4736.

Yes, sorry that was a misfire that I have now corrected.

I am not super worried about it since the longer isn't my "precision " ar but you know it's hard to shake it once you have rifles that are really accurate. I want the other one to be accurate too but you are right, the glass on the longer spaced one isn't even one you can shoot tiny groups with. It still bugs me if a rifle isn't pretty accurate.

 

[BuildingConceptsllc]

Anyone ever polished a bolt face to remove a thousandth or two?

 

[buyobuyo]

Anyone ever polished a bolt face to remove a thousandth or two?

Polished, no. Machined, yes.

 

[BuildingConceptsllc]

Polished, no. Machined, yes.

Yeah, might be just as well to take 5 thou off the barrel if I'm getting into that. I was trying to think of a way for me to fix it myself and I don't have a metal lathe. I guess I will see what the smith says about it before I do anything else

 

[Snuby642]

Yeah I wondered if that was kind of excessive. I may contact the Smith and see what he says.

I did swap the bolts and it did help. I'm now at

1.4655. With the shorter

1.4680 with the longer.

That's close enough to where I can probably load it for .0015" under the longer and be good but I'm still wondering if that's enough to effect my accuracy and/or brass life???? Thoughts by all ITT are welcome.

Well if I'm reading right you plan on running 0.0015 headspace on your rounds in the big chamber?

If you shoot fast in hot weather that could be a problem. If you dont keep it clean in cold weather it will be a problem.

Dont mess with your precision rifle, put that bolt back in.

What you did was verify it was the chamber oversized.

The other still has a big chamber see if the smythe that put it together can find a bolt or bcg that brings it down preferably same as the other.

I got lucky with standard wylde chambers and 4 of 5 bolts.

 

[BuildingConceptsllc]

Well if I'm reading right you plan on running 0.0015 headspace on your rounds in the big chamber?

If you shoot fast in hot weather that could be a problem. If you dont keep it clean in cold weather it will be a problem.

Dont mess with your precision rifle, put that bolt back in.

What you did was verify it was the chamber oversized.

The other still has a big chamber see if the smythe that put it together can find a bolt or bcg that brings it down preferably same as the other.

I got lucky with standard wylde chambers and 4 of 5 bolts.

Yeah I know it puts me in a tough spot for sizing, it's right there on the edge for what you'd want.

I think I'm going to have to leave the bolts swapped. They are both fairly new but since they are lefty, it's not so easy to just see if I can find one that makes the longer chamber shorter. It's not easy to get lefty bolts to begin with.

If I do leave the bolts swapped, (which test firing showed everything to work in both rifles just as they had before), then I would be sizing the brass to .0045" under fired size on the CLE chamber. The new barrel chamber would then be .002" under. Ideally I'd like to be .0025-.003" under fired brass size for AR's, but it seems like doing it this way will work out ok.

The smith replied (which was super fast) and basically said his reamer is definitely right and still new and and my other one is the one that is wrong and/or old, which is why the other chamber is too short. He also said he wasn't a fan of swapping bolts for the reasons you could imagine but if it worked, it's hard for him to argue it.

He may be exactly right, I can only measure brass and with my stuff so I'm not going to dispute that and I don't think accuracy will be an issue. The possibility of clickers/stuck cases and premature brass failure is probably the only real worry. I just want them to be closer to the same size. My other AR chamber is also a little bigger than the CLE one.

 

[Snuby642]

@BuildingConceptsllc

I think your builder is full of it.

I process thousands of rounds from the range for my use. Overwhelmingly 1.4640 and 1.4635 is what I come home with unless they ran a bunch of full automatic which needs a larger chamber for heating up I suppose.

This is from any brand you could imagine, with few home builds such as mine. And you can look up go - nogo .

That's were I get my "normal" expectations from .

Imho

 

[BuildingConceptsllc]

Yeah but I need to measure it with my other set. Right now my measurements are with the UR sets that I have but they give a little different measurement than my hornady set. I've sold my 419 and forster set so hornady and UR is all I have left and I just keep the hornady because of all my old notes and measurements are with those hornady comparators. When I get the kids to bed I will check it out with the hornady ones and see.

You are correct that my other 2 ar's are both 1.464 or right at it but I haven't measured their brass with the UR set either.

 

[BuildingConceptsllc]

So I went and measured the fired brass from each with hornady comparators and the new barrels brass measures 1.466-1.467 (5 pieces ) and the CLE barrel measured 1.462-1.463. So now I have more useless info but at least my measurements are consistent. I guess I need to measure some of my gagues and see what they measure and then could convert it....

I'm seriously thinking about trying to polish that shorter chambers bolt out .002" and rolling with it. I need to think of a good way to do it and keep it square and flat though. Or find a machine shop that will do it for me. I'd just need to remove .002" from the bolt face only right?

 

[Snuby642]

I have checked my Hornady comparitor and when properly re-zeroed more accurate than expected according to a couple gauges. Supprise to me.

Stick with one set to cut mistakes.
The short chamber could be fixed eisily by reaming the barrel deeper to match. Depends on the type of barrel.

The long chamber is a problem.
I dont know where a +0.002 left hand bolt could be had or modified.

Take 0.002 off the face of the lugs? Above my paygrade.

Probably the reason your short chamber was more accurate was you were using factory ammo?

So it took up some of the slop.

 

[Snuby642]

You know that 1.469 is 0.002 thousands over no go gauge.

Your barrel is out of speck and the builder should replace it.

 

[BuildingConceptsllc]

I have checked my Hornady comparitor and when properly re-zeroed more accurate than expected according to a couple gauges. Supprise to me.

Stick with one set to cut mistakes.
The short chamber could be fixed eisily by reaming the barrel deeper to match. Depends on the type of barrel.

The long chamber is a problem.
I dont know where a +0.002 left hand bolt could be had or modified.

Take 0.002 off the face of the lugs? Above my paygrade.

Probably the reason your short chamber was more accurate was you were using factory ammo?

So it took up some of the slop.

Nah I almost never shoot factory ammo. I load everything I shoot. I don't switch back and forth with comparators, I just kept the hornady ones because my older notes are using those.

 

[BuildingConceptsllc]

You know that 1.469 is 0.002 thousands over no go gauge.

Your barrel is out of speck and the builder should replace it.

Yeah but I don't know that my measurements are accurate to spec. I know my measurements are consistent for sure but I haven't checked them vs a gauge yet. I do have gagues though and will do that today and report back.

 

[BuildingConceptsllc]

You know that 1.469 is 0.002 thousands over no go gauge.

Your barrel is out of speck and the builder should replace it.

I know it's confusing but with the hornady comp the new chamber did not measure that. It measured 1.467" which is long but within spec

 

[Snuby642]

The way I understand it 1.467 is a no go and a reject.

If you take it to a gunsmith and his nogo 1.467 goes in it's bad.

Someone didn't check thier work.

 

[MontanaMan]

The way I understand it 1.467 is a no go and a reject.

If you take it to a gunsmith and his nogo 1.467 goes in it's bad.

Someone didn't check thier work.

Well, maybe, maybe not.

The dimensions for HS on SAAMI 223 & NATO 5.56 are significantly different & it depends on what his reamer was. (See chart below & linked article)

But in either case, his reamer could be right, but he ran it in a tad too far if it was a 223.

But with regards to the OP's problem. IMHO, consistently working the brass by .004" is not a good idea & will definitely shorten life; the simplest solution is too keep the brass separate & size accordingly, maybe even get a 2nd sizing die to eliminate constantly re-setting it. But if you can/ want to deal with the shortened life & keep a close eye on the brass for any possible head separations, the situation you have will be fine.

New brass is typically anywhere from min HS spec to as much as - .005", so functionally, there is no issue. But I'd suggest checking the HS on any new brass, & if much below min HS, (below zero), then fire it first in your gun with the shortest HS. Firing -.005" new brass in a chamber that is +.005" HS is a lot of initial stretch................but it happens somewhere, every day.

Also, when checking HS on a given bolt/barrel, you should strip the bolt for more accurate results.

If you were to attempt in increase HS on a bolt, you need to remove stock from the back of the lugs, not the face, or you could deepen the depth of the face that the brass sits against. And on anything other than a manganese phos bolt, you would need a grinder as nitride, chrome or PVD really can't be cut any other way.

I have done it to manganese phos bolts to fit a bolt to a short HS barrel before by stoning the rear of the lugs individually by hand & setting the lug dimensions all to the necessary dimension by measuring each one as they are stoned.....................not something you want to do everyday. So if you need to increase HS by .002" for example, you would need to remove .002" from the rear of the lugs.

See info below.

MM

HS Discussion & Info

 

[BuildingConceptsllc]

Thank you for the information, I do appreciate that. I'm not going to go messing the lugs and probably wouldn't even be able to get .002 off the bolt face.

My GO says "1.464" and measures at 1.462" in my calipers and comp.

My NO-go says "1.470"
and measures at 1.468" in my calipers and comp.

Field says " 1.474"
and measures at 1.472" in my calipers and comp.

The new barrel brass with the bolts swapped now measures 1.4665"

And the CLE measures 1.464"

(Of course we know that both of these measurements are actually .002" longer than this brass measurement is showing due to my calipers/comp. So 1.4685" and 1.4665" respectively.

So, I think my smith is right and the other CLE barrel just had a short chamber and his chamber is on the very end of being within spec, but it is within spec so....

Moral of the story.... ask and send a piece of brass or do something so your chambers are the same length.

The question now is.... "Do I mess with my CLE barrel and try to get the chamber made .002" longer to get them the same? And who knows how long that will take.

 

[MontanaMan]

Thank you for the information, I do appreciate that. I'm not going to go messing the lugs and probably wouldn't even be able to get .002 off the bolt face.

My GO says "1.464" and measures at 1.462" in my calipers and comp.

My NO-go says "1.470"
and measures at 1.468" in my calipers and comp.

Field says " 1.474"
and measures at 1.472" in my calipers and comp.

The new barrel brass with the bolts swapped now measures 1.4665"

And the CLE measures 1.464"

(Of course we know that both of these measurements are actually .002" longer than this brass measurement is showing due to my calipers/comp. So 1.4685" and 1.4665" respectively.

So, I think my smith is right and the other CLE barrel just had a short chamber and his chamber is on the very end of being within spec, but it is within spec so....

Moral of the story.... ask and send a piece of brass or do something so your chambers are the same length.

The question now is.... "Do I mess with my CLE barrel and try to get the chamber made .002" longer to get them the same? And who knows how long that will take.

Leave the CLE barrel alone; you are at minimum HS...................not exactly ideal in a semi-auto, but most factory ammo is below that number & if you get some a thou or 2 over that, it will crush fit.

Since you are now only 2.5 thou different, so size to the larger chamber plus .001" & you will be fine in both guns.

MM

 

[BuildingConceptsllc]

Leave the CLE barrel alone; you are at minimum HS...................not exactly ideal in a semi-auto, but most factory ammo is below that number & if you get some a thou or 2 over that, it will crush fit.

Since you are now only 2.5 thou different, so size to the larger chamber plus .001" & you will be fine in both guns.

MM

Yeah with primers out they are fairly close now, close enough to probably be ok. I wish they were closer but fortunately the bolt swapping helped out.

I never shoot factory ammo so I'm not all that concerned about that part, mainly just what to size to and not kill my brass after a few loads

 

[MontanaMan]

Next time you order a barrel from a custom source, just send the bolt you plan to use & tell them how much HS above zero that you want.

Or buy a bolt from them.

Most commercially produced barrel/extensions/chambers & bolts will end up at +.002-.004" HS when assembled together.

You have 2 barrels that don't conform to the mass produced specs.

Kind of an unusual problem.

MM

 

[BuildingConceptsllc]

Next time you order a barrel from a custom source, just send the bolt you plan to use & tell them how much HS above zero that you want.

Or buy a bolt from them.

Most commercially produced barrel/extensions/chambers & bolts will end up at +.002-.004" HS when assembled together.

You have 2 barrels that don't conform to the mass produced specs.

Kind of an unusual problem.

MM

I did. I sent the whole upper but I didn't tell him anything other than a "CLE" chamber which he said he had the reamer for.

 

[MontanaMan]

I did. I sent the whole upper but I didn't tell him anything other than a "CLE" chamber which he said he had the reamer for.

Sounded like CLE set the HS to zero. Not wrong for a precision gun, but tighter than you would normally get from separately bought components.

And your smith fitted the other one to a dimension near max.

Worst combo you could have gotten.........one long, one short.

Who'd a thunk it? LOL

MM

 

[BuildingConceptsllc]

Sounded like CLE set the HS to zero. Not wrong for a precision gun, but tighter than you would normally get from separately bought components.

And your smith fitted the other one to a dimension near max.

Worst combo you could have gotten.........one long, one short.

Who'd a thunk it? LOL

MM

Yeah that's about the size of it, as we say down here. I should have said something about my other one being short because I knew it was a little bit short I just wasn't thinking about it at the time. I sent it to them and then they actually did it months later so I just didn't think about it.

 

[Snuby642]

I give up.

I think B C got screwed on the crappy oversized barrel and should ask for a replacement.

There is no amount of white washing that can explain away a shit job.

If not, make sure others know who to avoid for gunwork.

 

[MontanaMan]

Actually, I wouldn't want it either, because I really don't want new factory brass to stretch that much either.

But BC says he doesn't shoot factory ammo so it's his call.

A local smith would have to do LOTS of AR barrels before I'd use one.

Besides just the actual chambering, getting good extensions & getting them timed & installed correctly takes some experience.

JMHO, YMMV

MM

 

[BuildingConceptsllc]

Actually, I wouldn't want it either, because I really don't want new factory brass to stretch that much either.

But BC says he doesn't shoot factory ammo so it's his call.

A local smith would have to do LOTS of AR barrels before I'd use one.

Besides just the actual chambering, getting good extensions & getting them timed & installed correctly takes some experience.

JMHO, YMMV

MM

It's not a local smith and is definitely extremely experienced. That's one reason I was more lax about sending it and not giving a ton of instructions ect but it's not a huge deal at this point with the bolt swapping working out the way it did. I wouldn't let a local smith do ANYTHING I wanted any precision out of. The barrel shoots great and everything else with the fit and finish is great from what I've seen of it. Like I said, I sent the whole upper (mainly so I didn't have to fool with it and was confident in how it would be installed ect)