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Posted: 4/12/2014 7:55:31 AM EDT
| What is the difference between the filed gauge and No-Go gauge? I looking to get some gauges to have and not sure which ones I should have. Do I need all three (go, no go and field) or do I only need a field gauge or would a go and no go be enough? |
| I went with the no-go gauge. When checking a new set up, I check with the no-go. If the bolt closes, I add scotch tape on the end of the gauge until is won't close and then add up the pieces of tape (usually .002" per piece) and add that to the gauge measurement to see how far out it is. If the bolt doesn't close on the no-go gauge, I use a factory round and see if the bolt will close. If it does, I'm go to go. I do these checks before installing the barrel. I guess you could do the same with only a go gauge to eliminate using a live round, if you've already have an installed barrel. |
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Would help to know what you want the gauges for in the first place.
If you are chamber'g barrels and checking side wall dimension widths, then the go, no-go gauges are not the gauges you want. If you are just checking to make sure that the head space is not too tight, or not too worn out, then the go and no-go gauges will work fine. Hence if the head space it too tight, the go gauge will not fit. If the head space is too loose (such as in a worn out bolt/chamber), it will allow the bolt to close (closed by hand with the extractor/ejector removed, and not the bolt slamming home instead) on a no-go gauge instead. |
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The headspace specs are different for 223 REM and 5.56 NATO.
In general Go and No-go to check a new barrel, the Field gage is supposed to be the max safe headspace. The disconnect here is the 223 REM Field gage is shorter than what SAAMI shows as the max chamber headspace. In fact the 223 REM Field gage is very close to the 5.56 NATO No-go gage. This is not the case for a 5.56 NATO Field gage. A weapon that fails this gage should not be fired. |
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Quoted:
Would help to know what you want the gauges for in the first place. If you are chamber'g barrels and checking side wall dimension widths, then the go, no-go gauges are not the gauges you want. If you are just checking to make sure that the head space is not too tight, or not too worn out, then the go and no-go gauges will work fine. Hence if the head space it too tight, the go gauge will not fit. If the head space is too loose (such as in a worn out bolt/chamber), it will allow the bolt to close (closed by hand with the extractor/ejector removed, and not the bolt slamming home instead) on a no-go gauge instead. I am more or less looking to get them to add to the tool box for down the road when/if I need to replace a bolt or install a new barrel. So use would be for this or to check my current set up to make its not too worn out like you mention. So if I got the Go and No-Go I should be covered for a quick check to assure everything is good to go? |
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223 Remington gauges and 5.56 NATO gauges are the exact same gauge. the only difference is in the barrels and it is the amount of freebore that is the difference. 5.56 NATO has a longer freebore than 223 Remington and because of this freebore, chamber pressure will be lower. it is recommended that 5.56 ammo not be fired in 223 rem barrels, because of the difference in chamber pressures with NATO spec ammo which is developed and tested in 5.56 NATO test barrels/chambers. the cartridge dimensions are identical. just to add to the confusion, some manufacturers have a 223 wylde marked barrel. this is a 223/5.56 NATO chamber with an inbetween freebore. the freebore is longer than 223, but shorter than 5.56 NATO, and can safely shoot both types of ammo. barrels marked 5.56 NATO can also shoot 223 Remington ammo and 5.56 NATO ammo safely. the only caution is not to shoot 5.56 NATO ammo in a 223 Remington stamped barrel as the pressures may be excessive.
regarding gauges... a go gauge is the minimum spec chamber, a field gauge is the maximum allowable headspace, and a no go is excessive headspace. if your bolt closes on a field gauge, please check it again with a no go gauge, because it is very close to being excessive headspace. your rifle needs attention soon when the bolt closes on the field gauge. |
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I have to somewhat disagree.
If a barrel fails the NATO field gage (1.4736”) then it is no longer safe to fire. If a barrel fails a No-go gage then it should be checked with a Field gage. If it passes the Field gage then it is still safe to fire. SAAMI 223 REM No-go (AFAIK current) 1.4666”. US Mil-spec No-go 1.4706”. |
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Quoted:
I have to somewhat disagree. If a barrel fails the NATO field gage (1.4736”) then it is no longer safe to fire. If a barrel fails a No-go gage then it should be checked with a Field gage. If it passes the Field gage then it is still safe to fire. SAAMI 223 REM No-go (AFAIK current) 1.4666”. US Mil-spec No-go 1.4706”. there is a pdf here, if it doesn't hotlink please do so or imbed for me, I am computer challenged www.ar15barrels.com/data/headspace.pdf the issue I have with the info is why does the field gauge have a larger dimension than the no go gauge? shouldn't it be the other way around? I'm baffled. |
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That PDF is out of date to some degree.
The current terminology has been in use for a very long time. The specs associated with the terminology can vary between calibers and the originating organizations for the specs. In a Go, No-go, and Field series of gages the Field gage is the largest dimension. That is just the way it is, why should it be the other way around? |
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Quoted:
That PDF is out of date to some degree. The current terminology has been in use for a very long time. The specs associated with the terminology can vary between calibers and the originating organizations for the specs. In a Go, No-go, and Field series of gages the Field gage is the largest dimension. That is just the way it is, why should it be the other way around? OK, thanks for setting me straight, I appreciate the guidance. |
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PFC,
You know what is odd is looking at the SAAMI cartridge dimensions from bolt-face to .330 datum line. The spec is 1.4666" - 00.70". Now, if you add .0070" to 1.4666" it ends up equaling 1.4706". But, SAAMI No-go is 1.4666" which is the longest a .223 cartridge will be that is within spec. SAAMI .223 REM Max. Cartridge / Min. Chamber I wonder if the military specification for headspace when it was first written for the M16 was a typographical error when they specified the dimension for maximum headspace (No-go) of 1.4706" for a new barrel that has been high pressure tested? |
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PFC, You know what is odd is looking at the SAAMI cartridge dimensions from bolt-face to .330 datum line. The spec is 1.4666" - 00.70". Now, if you add .0070" to 1.4666" it ends up equaling 1.4706". But, SAAMI No-go is 1.4666" which is the longest a .223 cartridge will be that is within spec. SAAMI .223 REM Max. Cartridge / Min. Chamber I wonder if the military specification for headspace when it was first written for the M16 was a typographical error when they specified the dimension for maximum headspace (No-go) of 1.4706" for a new barrel that has been high pressure tested? US military weapons seem to have a lot more headspace tolerance than the civilian equivalents. However I can’t disagree as allowing that much of the available headspace to be gone in a new barrel seems fairly excessive to me. Seems like that spec was set back in the day when Colt and Olin had a lot of political clout. Anyone that takes the time to follow your SAAMI link should come away with a new appreciation for the importance of the Go gage. |
| Remember that the proper headspace spec to use is dependent on both the chamber as well as the cartridge to be fired. Since the Military only fires 5.56 NATO which uses a harder brass than .223 commercial loads, it can handle a longer headspace as the brass doesn't stretch as much. But an AR-15 sold on the commercial market will fire .223 and 5.56 as well as steel cased imported ammo and reloads. This is why rifles for the commercial market are factory headspaced to .223 SAAMI specs and not 5.56. Most barrel and bolt combos on the market will just close on a .223 GO, but there are some exceptions. I wouldn't want a new barrel and bolt combo to fails a .223 NOGO as that means it's that much closer to failing a field gauge. There's no need for that much headspace on a semi-auto, it negatively effects accuracy. |
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Quoted:
I am more or less looking to get them to add to the tool box for down the road when/if I need to replace a bolt or install a new barrel. So use would be for this or to check my current set up to make its not too worn out like you mention. So if I got the Go and No-Go I should be covered for a quick check to assure everything is good to go? Quoted:
Quoted:
Would help to know what you want the gauges for in the first place. If you are chamber'g barrels and checking side wall dimension widths, then the go, no-go gauges are not the gauges you want. If you are just checking to make sure that the head space is not too tight, or not too worn out, then the go and no-go gauges will work fine. Hence if the head space it too tight, the go gauge will not fit. If the head space is too loose (such as in a worn out bolt/chamber), it will allow the bolt to close (closed by hand with the extractor/ejector removed, and not the bolt slamming home instead) on a no-go gauge instead. I am more or less looking to get them to add to the tool box for down the road when/if I need to replace a bolt or install a new barrel. So use would be for this or to check my current set up to make its not too worn out like you mention. So if I got the Go and No-Go I should be covered for a quick check to assure everything is good to go? Yes. Go and No Go will do what you are asking them to do. |
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Quoted:
I am more or less looking to get them to add to the tool box for down the road when/if I need to replace a bolt or install a new barrel. So use would be for this or to check my current set up to make its not too worn out like you mention. So if I got the Go and No-Go I should be covered for a quick check to assure everything is good to go? Quoted:
I am more or less looking to get them to add to the tool box for down the road when/if I need to replace a bolt or install a new barrel. So use would be for this or to check my current set up to make its not too worn out like you mention. So if I got the Go and No-Go I should be covered for a quick check to assure everything is good to go? Or, if you have trust in the folks at BCM, you could follow their advice: (This is a direct quote from them, copied from TOS;) 3) A little knowledge is dangerous, but if you must mess around with a headspace gauges get a FIELD gauge. That is the only one you will need. That is the only one you will need. Not just any field gauge, get the NATO one that Colt recommends (.1.4736”)(Brownells #319-418-033). You are not building barrels, you are not fitting bolts. You are in “the field”, and that is your gauge.
Double check the measurements on your gauge. I have seen many gauges with text and not marked with a numeric measurement and even mismarked dimentions. Get rid of them. Just keep the Colt FIELD Gauge The one highlighted in red is the one I have always used. And, like you, since all I need to know is "is it safe to fire", it's all I have ever needed. |
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Quoted:
Or, if you have trust in the folks at BCM, you could follow their advice: (This is a direct quote from them, copied from TOS;) The one highlighted in red is the one I have always used. And, like you, since all I need to know is "is it safe to fire", it's all I have ever needed. Quoted:
Quoted:
I am more or less looking to get them to add to the tool box for down the road when/if I need to replace a bolt or install a new barrel. So use would be for this or to check my current set up to make its not too worn out like you mention. So if I got the Go and No-Go I should be covered for a quick check to assure everything is good to go? Or, if you have trust in the folks at BCM, you could follow their advice: (This is a direct quote from them, copied from TOS;) 3) A little knowledge is dangerous, but if you must mess around with a headspace gauges get a FIELD gauge. That is the only one you will need. That is the only one you will need. Not just any field gauge, get the NATO one that Colt recommends (.1.4736”)(Brownells #319-418-033). You are not building barrels, you are not fitting bolts. You are in “the field”, and that is your gauge.
Double check the measurements on your gauge. I have seen many gauges with text and not marked with a numeric measurement and even mismarked dimentions. Get rid of them. Just keep the Colt FIELD Gauge The one highlighted in red is the one I have always used. And, like you, since all I need to know is "is it safe to fire", it's all I have ever needed. Yes, If you are in he field and want to see if the chamber is a safe size then the field gauge is the way to go. If you are fitting bolts you will want the Go and No Go. Here is a really good link from Forster. http://www.forsterproducts.com/client_images/catalog19938/pages/files/Headspace_Gage_Instructions.pdf |
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Quoted:
Yes, If you are in he field and want to see if the chamber is a safe size then the field gauge is the way to go. If you are fitting bolts you will want the Go and No Go.... True, but since the OP seems to only want to verify the safety of a given rifle, all he really needs is the Field Gauge. Since very few of us possess the tools and ability to actually adjust or correct the headspace on an AR we really don't need the Go and No-Go gauges. If a rifle chambers a round without issues, and passes the Field Gauge test, it's good to go. Again, and I don't mean to be contrary, but I believe the folks at BCM offer good advice that would apply to 95% of us. |
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True, but since the OP seems to only want to verify the safety of a given rifle, all he really needs is the Field Gauge. Since very few of us possess the tools and ability to actually adjust or correct the headspace on an AR we really don't need the Go and No-Go gauges. If a rifle chambers a round without issues, and passes the Field Gauge test, it's good to go. Again, and I don't mean to be contrary, but I believe the folks at BCM offer good advice that would apply to 95% of us. Quoted:
Quoted:
Yes, If you are in he field and want to see if the chamber is a safe size then the field gauge is the way to go. If you are fitting bolts you will want the Go and No Go.... True, but since the OP seems to only want to verify the safety of a given rifle, all he really needs is the Field Gauge. Since very few of us possess the tools and ability to actually adjust or correct the headspace on an AR we really don't need the Go and No-Go gauges. If a rifle chambers a round without issues, and passes the Field Gauge test, it's good to go. Again, and I don't mean to be contrary, but I believe the folks at BCM offer good advice that would apply to 95% of us. Not really, A field gauge is used on a rifle that you know that started off with the correct head space, and need to test the chamber down the road of a lot of use to see if the wear to the chamber is excessive, and if the barrel needs to be take out of service (hence chamber will swallow the gauge). On a new barrel, a no gauge gauge will tell you if the head space it too long (if the bolt locks up), while on the go gauge, will tell you if the head space is too short instead (bolt will not lock up it). Simply, with a chamber that is too tight in head space, you can still get a the bolt to lock up on a round since the brass will give as the bolt slams home, but will cause all kind of short stroking problems that you might not pick up other wise. |
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Quoted:
True, but since the OP seems to only want to verify the safety of a given rifle, all he really needs is the Field Gauge. Since very few of us possess the tools and ability to actually adjust or correct the headspace on an AR we really don't need the Go and No-Go gauges. If a rifle chambers a round without issues, and passes the Field Gauge test, it's good to go. Again, and I don't mean to be contrary, but I believe the folks at BCM offer good advice that would apply to 95% of us. Quoted:
Quoted:
Yes, If you are in he field and want to see if the chamber is a safe size then the field gauge is the way to go. If you are fitting bolts you will want the Go and No Go.... True, but since the OP seems to only want to verify the safety of a given rifle, all he really needs is the Field Gauge. Since very few of us possess the tools and ability to actually adjust or correct the headspace on an AR we really don't need the Go and No-Go gauges. If a rifle chambers a round without issues, and passes the Field Gauge test, it's good to go. Again, and I don't mean to be contrary, but I believe the folks at BCM offer good advice that would apply to 95% of us. The OP posted: "I am more or less looking to get them to add to the tool box for down the road when/if I need to replace a bolt or install a new barrel. So use would be for this or to check my current set up to make its not too worn out like you mention. So if I got the Go and No-Go I should be covered for a quick check to assure everything is good to go?" That is what I was responding to. I think Go and No Go gauges may help him beyond what a Field gauge might do. All are good, just different. And BCM is a great company. Gator, you can have the last word. |
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