ChronoCube
Member
When checking headspace of milsurp bolt action rifles, is using a "field" gauge sufficient? i.e. without using a "go" or a "no-go" gauge as well.
Thanks.
Thanks.
Question about headspace gauges
- Thread starter ChronoCube
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dagger dog
Member
The name is what it is field, the gauge that you want to take with you when you are going to purchase a new used rifle. If it closes on a feild gauge, then you know the headspace is out. The go, no go are used to set up a new barrel,bolt receiver, and also to check out short and long chambers.
wally
Member
Yes, when it closes on the field gauge it needs work and should not be shot. The go and no-go are for gunsmiths to set min-max headspace for a long service life.
--wally.
--wally.
ChronoCube
Member
In that case, would a .308 field gauge work for rifles chambered in 7.62x51 (military), such as the Ishapore 2A?
Maverick223
Member
Yep, the gauge doesn't care what the pressure standards for the cartridge are.
"In that case, would a .308 field gauge work for rifles chambered in 7.62x51 (military), such as the Ishapore 2A?"
According to some notes I took from someplace on the web years ago, a 7.62X51 rifle could swallow a 308 Winchester field gauge and still be good to go:
7.62x51mm NATO Go 1.6355"
7.62x51mm NATO Field Reject 1.6455"
7.62x51mm NATO minimum cartridge headspace 1.630
7.62x51mm NATO maximum cartridge headspace 1.633
7.62x51mm NATO average cartridge headspace 1.6315
.308 Winchester Go 1.630"
.308 Winchester No Go 1.634"
.308 Winchester Field Reject 1.638"
.308 Winchester minimum cartridge headspace 1.627
.308 Winchester maximum cartridge headspace 1.633
.308 Winchester average cartridge headspace 1.630
Tim
According to some notes I took from someplace on the web years ago, a 7.62X51 rifle could swallow a 308 Winchester field gauge and still be good to go:
7.62x51mm NATO Go 1.6355"
7.62x51mm NATO Field Reject 1.6455"
7.62x51mm NATO minimum cartridge headspace 1.630
7.62x51mm NATO maximum cartridge headspace 1.633
7.62x51mm NATO average cartridge headspace 1.6315
.308 Winchester Go 1.630"
.308 Winchester No Go 1.634"
.308 Winchester Field Reject 1.638"
.308 Winchester minimum cartridge headspace 1.627
.308 Winchester maximum cartridge headspace 1.633
.308 Winchester average cartridge headspace 1.630
Tim
Maverick223
Member
Hmm, with the brass being the same size I figured it would be the same, but I didn't take into account the somewhat loose tolerances of some 7.62NATO "battle rifles". Thanks for the clarification.
ChronoCube
Member
Also, which brands of gauges require removal of firing pin & extractor?
"Also, which brands of gauges require removal of firing pin & extractor?"
All the commercial gauges that I have seen do. I understand that some gauges have been made, mostly for military armorers, that have cutouts for the extractor and ejector, but I have never seen one for sale. Presumably these gauges are made to fit only one type of rifle.
If, by chance, you are measuring an M1A/M14, you can remove the offending parts without disassembling the rifle. With the magazine out, put a fired 30-06 case under the extractor and chamber it. It is too long, and will stick out about 1/2 inch, but it holds the ejector in, so you can drive out the pin if you flip the rifle over and use a punch of some sort from the bottom. Be ready to catch it, and be aware that your firing pin is now floating around loose in there, so be careful.
Tim
All the commercial gauges that I have seen do. I understand that some gauges have been made, mostly for military armorers, that have cutouts for the extractor and ejector, but I have never seen one for sale. Presumably these gauges are made to fit only one type of rifle.
If, by chance, you are measuring an M1A/M14, you can remove the offending parts without disassembling the rifle. With the magazine out, put a fired 30-06 case under the extractor and chamber it. It is too long, and will stick out about 1/2 inch, but it holds the ejector in, so you can drive out the pin if you flip the rifle over and use a punch of some sort from the bottom. Be ready to catch it, and be aware that your firing pin is now floating around loose in there, so be careful.
Tim
http://www.geocities.com/yankeeengineers/products.html
These guys make gauges that do not require removal of the firing pin & extractor. However, the gauges are more rifle specific because of this, so you may not be able to find the gauge you need.
A quick google search for "coin headspace gauge" turned up another company called Okie that also has gauges, though I haven't found their main page yet.
Hope this helps
EDIT: I just read that these style of gauges only work for rifles that accept a rimed cartridge. So if you are looking for a gauge for a rimless cartridge, then this really wont work. Oh well. I'm still gonna get one for my mosin
These guys make gauges that do not require removal of the firing pin & extractor. However, the gauges are more rifle specific because of this, so you may not be able to find the gauge you need.
A quick google search for "coin headspace gauge" turned up another company called Okie that also has gauges, though I haven't found their main page yet.
Hope this helps
EDIT: I just read that these style of gauges only work for rifles that accept a rimed cartridge. So if you are looking for a gauge for a rimless cartridge, then this really wont work. Oh well. I'm still gonna get one for my mosin
Doggy Daddy
Member
This is why my HRA M14 barrel swallowed a commerical field reject gage. I put that barrel on new M1a receiver and freaked when the bolt closed, with a lot of slop, on commerical field reject gage.
A military friend of mine verified that a batch of fresh Arsenal rebuild M14's that he inspected, swallowed his field reject gages.
Sorry to bring up an old thread, but I am new to checking headspace. Does everyone own headspace gauges for every caliber they own? Is it more important to check headspace on certain guns? It seems like it could get expensive to buy gauges for several different calibers.
Maverick223
Member
I don't own a single one...they are unnecessary for all modern rifles that have not been tampered with or shot the heck out of. OTOH they are useful for surplus rifles because these typically exhibit a high degree of wear and the state of repair is generally unknown. The few times I have been concerned with headspace I just took it to a smith to have it checked out.
You need to check headspace when swapping bolts and buying surplus rifles
There is some bad info on this thread.
You need a minimum of a Go Gauge and a Field, preferably all three gauges
If swapping bolts you need to make sure the bolt will close on a Go Gauge, if it doesnt you have a dangerous situation as there is not enough headspace. Should also be checked on any surplus rifle as you dont know that bolt hasnt been swapped out and not checked
Next is a No Go Guage which preferably it will not close on. If it does close all is not lost. Check next with a Field guage, if bolt does not close you must closely monitor the headspace as you shoot the weapon as it is close to getting out of spec
There is some bad info on this thread.
You need a minimum of a Go Gauge and a Field, preferably all three gauges
If swapping bolts you need to make sure the bolt will close on a Go Gauge, if it doesnt you have a dangerous situation as there is not enough headspace. Should also be checked on any surplus rifle as you dont know that bolt hasnt been swapped out and not checked
Next is a No Go Guage which preferably it will not close on. If it does close all is not lost. Check next with a Field guage, if bolt does not close you must closely monitor the headspace as you shoot the weapon as it is close to getting out of spec
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Vern Humphrey
Member
For a semi-auto, yes. You could have a slam-fire, with the firing pin continuing forward with enough force to fire the round while the bolt fails to lock.
For a bolt rifle, no. If the bolt will not close on the Go Gauge, it will not close on a properly-dimensioned round and will not fire.
Be advised with certain rifles, like Enfields for instance, they are measured using mil-spec gauges, not SAMMI. The SAMMI field gauge is about equivalent to the mil-spec "no go" gauge. I had to get a "mil-spec" field grade gauge specially ground since I couldn't find any for sale.
Innovative
Member
You can measure chamber clearance ...
There's no need for go/no-go gauges unless you're fitting a barrel for the first time.
Keep in mind that you can always compare one of your fired cases (at the shoulder) to one of your resized cases. This allows you to set your FL die height accurately. Your handloads will then fit perfectly, and case stretching will be minimized.
- Innovative
There's no need for go/no-go gauges unless you're fitting a barrel for the first time.
Keep in mind that you can always compare one of your fired cases (at the shoulder) to one of your resized cases. This allows you to set your FL die height accurately. Your handloads will then fit perfectly, and case stretching will be minimized.
- Innovative
What if you dont have enough headspace because someone didnt check headspace and swapped out the bolt???
For instance in Garands differnt lot bolts are slightly different lengths. Say a rifle had a shorter bolt then someone came along and swapped it out for a longer bolt????? You are asking for trouble
When swapping bolts in semi autos or buing a surplus semi auto its only smart to check with both ne NO and No GO gauge.
You say you only need a Field gauge, would you pay the same amount for a rifle that is almost closed on a Field or has plenty of room on a NO GO gauge?
The Field guage is the absolute largest headspace a rifle can SAFELY have. It is at the end of its useful life and must be closely monitured
For instance in Garands differnt lot bolts are slightly different lengths. Say a rifle had a shorter bolt then someone came along and swapped it out for a longer bolt????? You are asking for trouble
When swapping bolts in semi autos or buing a surplus semi auto its only smart to check with both ne NO and No GO gauge.
You say you only need a Field gauge, would you pay the same amount for a rifle that is almost closed on a Field or has plenty of room on a NO GO gauge?
The Field guage is the absolute largest headspace a rifle can SAFELY have. It is at the end of its useful life and must be closely monitured
Innovative
Member
Orlando .......
You're right. Changing the bolt on ANY rifle will often change the headspace. However, swapping a bolt isn't done very often. It's a good practice to measure the clearance (at the shoulder) that YOUR handloads have in YOUR particular chamber. This provides the information to set your die height more accurately, and that makes your cases last a lot longer. It also eliminates the chance for headspace separation.
- Innovative
You're right. Changing the bolt on ANY rifle will often change the headspace. However, swapping a bolt isn't done very often. It's a good practice to measure the clearance (at the shoulder) that YOUR handloads have in YOUR particular chamber. This provides the information to set your die height more accurately, and that makes your cases last a lot longer. It also eliminates the chance for headspace separation.
- Innovative
I am in agreement with you on modern rifles.
On surplus rifles it is very common for bolts to be swapped . Alot of times rifles are Imported into the US without bolts in them, then bolts installed. Hopefully the Importer checks headspace.
Bolts are also swapped by collectors to make a rifle "correct"
Using a properly sized case would work for a go gauge but if the common shooter doesnt have a set of gauges I doubt he has reloading equipment
On surplus rifles it is very common for bolts to be swapped . Alot of times rifles are Imported into the US without bolts in them, then bolts installed. Hopefully the Importer checks headspace.
Bolts are also swapped by collectors to make a rifle "correct"
Using a properly sized case would work for a go gauge but if the common shooter doesnt have a set of gauges I doubt he has reloading equipment
Innovative
Member
Wow ....... with ammo prices the way they are today ....... I thought every shooter was reload his own ammo. I only know one shooter that doesn't reload. (He's very wealthy.)
- Innovative
- Innovative
Hi, Orlando,
So what if the bolt closes on a NO-GO? Most rifles that have seen significant use will do so. There is no danger unless the rifle swallows a Field gauge.
Also, you wrote, "If swapping bolts you need to make sure the bolt will close on a Go Gauge, if it doesnt you have a dangerous situation as there is not enough headspace."
What dangerous situation? The worst that happens is that the bolt won't close, a possible disastrous situation in combat, but not one to be "dangerous" in the normal sense of the word in civilian use. If the bolt closes, the cartridge will fire normally, no matter how tightly the cartridge fits.
(The above assumes a cartridge supported (headspaced) on the shoulder, not on the rim.)
Jim
So what if the bolt closes on a NO-GO? Most rifles that have seen significant use will do so. There is no danger unless the rifle swallows a Field gauge.
Also, you wrote, "If swapping bolts you need to make sure the bolt will close on a Go Gauge, if it doesnt you have a dangerous situation as there is not enough headspace."
What dangerous situation? The worst that happens is that the bolt won't close, a possible disastrous situation in combat, but not one to be "dangerous" in the normal sense of the word in civilian use. If the bolt closes, the cartridge will fire normally, no matter how tightly the cartridge fits.
(The above assumes a cartridge supported (headspaced) on the shoulder, not on the rim.)
Jim
Go back and read what I posted
As I already stated twice, the No Go Gauge is what I would use to check headspace, If it closes on the No Go check it with the Field guage if it passes you need to keep a close eye on headspace as you are getting close to the end of its useful life and will need to be replaced in near future.
Agin like I said before, Which would you rather have a rifle that doesnt close on a No Go or on a Field gauge. Its pretty easy decision
A rifle(semi auto) that does not close on a Go gauge can fire out of battey,. I'm still looking for the picture
As I already stated twice, the No Go Gauge is what I would use to check headspace, If it closes on the No Go check it with the Field guage if it passes you need to keep a close eye on headspace as you are getting close to the end of its useful life and will need to be replaced in near future.
Agin like I said before, Which would you rather have a rifle that doesnt close on a No Go or on a Field gauge. Its pretty easy decision
A rifle(semi auto) that does not close on a Go gauge can fire out of battey,. I'm still looking for the picture
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