Headspace gauge length 308 1.634 or 1.636 No Go.

[Thumper580]

I bought a Ballistic Advantage AR10 308 heavy Modern series barrel. I have a new set of Clymer 308 gauges. Go 1.630......No Go 1.634. The bolt closes on the Go gauge and also on the No Go (1.634). I called Ballistic Advantage and told them about it. They told me they use PTG No Go gauges that are 1.636... and that barrel is fine.
Not sure if I should be worried or it's fine. I know the BCG has to open and close, but I feel for accuracy it would be better to be a little "closer". I never plan to shoot NATO ammo through it... Handloads with Lapua, Eagle or FC brass. Thoughts? Thanks.

 

[KYAggie]

Put a piece of scotch tape on the end of your 1.634 no-go gage and effectively turn it into a 1.636 no-go gage. See if your bolt closes on it. If it does, I would say you might have a problem. Put another piece of tap on and try again.

If it does not close with one piece of tape, you’ll probably be ok, but you will want to set up your resizing die so it doesn’t set the shoulder back too much and over work the brass.

 

[45-90]

I bought a Ballistic Advantage AR10 308 heavy Modern series barrel. I have a new set of Clymer 308 gauges. Go 1.630......No Go 1.634. The bolt closes on the Go gauge and also on the No Go (1.634). I called Ballistic Advantage and told them about it. They told me they use PTG No Go gauges that are 1.636... and that barrel is fine.
Not sure if I should be worried or it's fine. I know the BCG has to open and close, but I feel for accuracy it would be better to be a little "closer". I never plan to shoot NATO ammo through it... Handloads with Lapua, Eagle or FC brass. Thoughts? Thanks.

I have Forester go and no go gauges... they are made to exacting dimensions, no matter who grinds the gauge.
Does it say 308 Win on the barrel or 7.62 Nato? To know what it is exactly chambered for...
So:
308 go gauge 1.630"
308 no go gauge 1.634"
308 field gauge 1.638"
So for 308 Win 1.638" field gauge IS the max chamber length to safely fire the cartridge and use.
If a 308 chamber its probably fine, I used a factory Rem 700, no go chambered 308 rifle for 8000rds before changing the barrel.
It should not close on a standard no go with 2 pieces of trimmed scotch tape on the head of the gauge ...it would be better if the bolt wouldn't close on one added piece of tape.
Next:
A 7.62X51 Nato chamber:
Go gauge 1.635"
No go 1.6405"
The military has a field gauge too 1.6455" and an "emergency use" gauge above that.
The armorer won't take your weapon in the middle of a firefight.
If you reload adjust your full length sizing die according to the length of "Your" longer chambered rifle...or experience case head separation, on multiple firings.
My 18" heavy fluted modern BA barrel was not the best for accuracy...with just one good load... was 168 gr Speer, 50.5 gr 2000 MR, 2690 fps, 11 S/D 10 shots into .972" none of the other more expensive bullets did even close...a one load wonder.
So I changed it for a Proof SS barrel...for better all around accuracy. Yours may be different, just my experience. Also note a nato go gauge used to chamber a 308 would have a longer end result...not saying they did or didn't but the mix up is possible, and miss leading about a different "brand" of gauge...they must all be ground the same if SAAMI chambered...that's what "standards" are set up for... So all the ammo for a particular caliber, chamber safety in all the firearms, chambered for it.

 

[supercorndogs]

Closing on a no go doesn't mean headspace is excessive, closing on a field gauge does. Probably more people should just have a field if they are worried about checking their headspace vs a go and no go set.

 

[45-90]

If closing on a field gauge has resistance at the close you are at the SAAMI max... safe to shoot, but...far from ideal.
Most gunsmiths have no trouble staying between the more acceptable & recommended limits between the "go" to "no- go" range. But a field gauge gun is good enough if you're unable to fix the problem yourself, just adjust your reloading die accordingly, just know there will be more brass stretch on the initial firing...probably not a problem for a non reloader, shoot and discard, or a 20 rd per yr hunter.

 

[Thumper580]

I have Forester go and no go gauges... they are made to exacting dimensions, no matter who grinds the gauge.
Does it say 308 Win on the barrel or 7.62 Nato? To know what it is exactly chambered for...
So:
308 go gauge 1.630"
308 no go gauge 1.634"
308 field gauge 1.638"
So for 308 Win 1.638" field gauge IS the max chamber length to safely fire the cartridge and use.
If a 308 chamber its probably fine, I used a factory Rem 700, no go chambered 308 rifle for 8000rds before changing the barrel.
It should not close on a standard no go with 2 pieces of trimmed scotch tape on the head of the gauge ...it would be better if the bolt wouldn't close on one added piece of tape.
Next:
A 7.62X51 Nato chamber:
Go gauge 1.635"
No go 1.6405"
The military has a field gauge too 1.6455" and an "emergency use" gauge above that.
The armorer won't take your weapon in the middle of a firefight.
If you reload adjust your full length sizing die according to the length of "Your" longer chambered rifle...or experience case head separation, on multiple firings.
My 18" heavy fluted modern BA barrel was not the best for accuracy...with just one good load... was 168 gr Speer, 50.5 gr 2000 MR, 2690 fps, 11 S/D 10 shots into .972" none of the other more expensive bullets did even close...a one load wonder.
So I changed it for a Proof SS barrel...for better all around accuracy. Yours may be different, just my experience. Also note a nato go gauge used to chamber a 308 would have a longer end result...not saying they did or didn't but the mix up is possible, and miss leading about a different "brand" of gauge...they must all be ground the same if SAAMI chambered...that's what "standards" are set up for... So all the ammo for a particular caliber, chamber safety in all the firearms, chambered for it.

It's a 308 on the Ballistic barrel.

 

[45-90]

It's a 308 on the Ballistic barrel.

Then it should definitely not close on a 308 field gauge, with no resistance..but if it easily closes on the 308 no go you should have the option to send it back for another 308 barrel, rather than accept it as is, even though it may be "in", but toward the max in headspace, without a field gauge. Easy to fix for someone who does chambering barrels for a living. And that should be part of their customer service. Send it back, you Are the customer.

 

[B y r o n]

SAAMI doesn't publish data for "Go, No-Go or Field gauges", it only publishes min and max chamber length. 308 Winchester show 1.630" for min and 1.640" for max. I haven't been able to find any source about what is standard Go, No-Go, Field dimensions.

 

[45-90]

SAAMI doesn't publish data for "Go, No-Go or Field gauges", it only publishes min and max chamber length. 308 Winchester show 1.630" for min and 1.640" for max. I haven't been able to find any source about what is standard Go, No-Go, Field dimensions.

SAAMI doesn't publish data on ammunition either, that I know of ... but that doesn’t mean it does not exist. The Ammo must be shorter than the least call out dimension on the chamber, 1.630" so it fits all chambers in all manufactured rifle for that standardized cartridge. The max is field gauge at 1.638" or .002" off max chamber in drawing.
But since the ammo must be shorter to fit minimum chamber 1.630", gunsmiths and manufacturers have a standard for go and no gauges printed on the gauges mine say 1.630" go to 1.634" no go, so a 1.627" factory round fits without excessive case stretch on initial firing.

 

[45-90]

When there are no gauges for your standard, obsolete, or wildcat... don't use them, and are not needed. Use your finish reamer and die to form a brass cartridge gauge to set your chamber depth to... as this is what you are actually firing brass cases with .001" to .002"clearence to datum line ...not gauges.

 

[BCP]

its probably closer to 7.62NATO which is fine if you wanted a certain headspace get a short chambered barrel and have it finish reamed to spec.

Tbh be glad it’s not too short which happens a lot with mixmaster 308 AR rifles.