Go NoGo Gauge Clarity

[Mram10us]

In the past year I started doing a lot of research about how to make my own headspace gauges. Read on the forums that they differ based on manufacturer. Called around and talk to numerous manufacturers stating the Go gauge is always tied to the minimum saami spec headspace shown in the picture below. NoGo gauges are not tied to a specific value and vary depending on cartridge and manufacturer. These are generally Go +.004-006", but again, no set value.

I bring this up because I caused some confusion the other day in the thread where JE Custom was mentioning head spacing zero-.0015" off of min spec. I asked if he went off the saami min spec or the go gauge itself. I shouldn't have said that because they are both one in the same with every manufacturer that I've talk to you. Again, the NoGo changes, but the Go is always associated with the min spec on the saami sheet. Sorry for any confusion I caused.

 

[YZ-80]

That's OK. Now I have a question: Just because a rifle closes on a No-go gage, does that necessarily mean that it is not safe to shoot? I'm sorry if that seems like a silly question but I had a rifle once that I had been shooting for years and when I went to sell it the dealer showed me that the rifle closed on a No-go gage. My jaw dropped - I had been shooting it for several years!

 

[Mram10us]

That's OK. Now I have a question: Just because a rifle closes on a No-go gage, does that necessarily mean that it is not safe to shoot? I'm sorry if that seems like a silly question but I had a rifle once that I had been shooting for years and when I went to sell it the dealer showed me that the rifle closed on a No-go gage. My jaw dropped - I had been shooting it for several years!

Not a silly question at all. You just need to know your headspace. If it closes on your NoGo, you only know it is at least ~.005" more than min headspace. Add a shim or tape to the NoGo to see where it will not close. A field gauge is another option. Big takeaway, you want to know what your headspace is.

 

[Dean2]

That's OK. Now I have a question: Just because a rifle closes on a No-go gage, does that necessarily mean that it is not safe to shoot? I'm sorry if that seems like a silly question but I had a rifle once that I had been shooting for years and when I went to sell it the dealer showed me that the rifle closed on a No-go gage. My jaw dropped - I had been shooting it for several years!

A Field Gauge is what is used to measure the max generally acceptable head space. This is a SAMI spec measurement. The No-Go gauge is just a suggestion and there is NO SAMI spec for a no-go gauge, there is for Go and Field however..

 

[J E Custom]

That's OK. Now I have a question: Just because a rifle closes on a No-go gage, does that necessarily mean that it is not safe to shoot? I'm sorry if that seems like a silly question but I had a rifle once that I had been shooting for years and when I went to sell it the dealer showed me that the rifle closed on a No-go gage. My jaw dropped - I had been shooting it for several years!

The No Go gauge is used to tell you that the chamber is large or the lugs are set back to the point that the rifle "Should not be shot" because of possible case head separation that could render the weapon inoperable. It doesn't mean that it is unsafe. The military sets this dimension to prevent issues in the field that could cause the soldier to have problems that could be life threatening.
Normally if the bolt closes slightly on a no go gauge it will only be hard on cases and may eventually cause problems.

Head space can be more than the .006 and the fact that the brass cases are ductile means that for a few shots you may get away with it, but the magnums are a different story and many recommend holding it to .004 max.

If you have a rifle that a no go gauge will close on, you can do minimum sizing (Just enough to chamber) and brass life will improve because the cases are no longer SAMMI dimension but will work in that chamber and That is .006 thousandths longer than a SAMMI chamber. It isn't the size of the chamber, it's the size of the cartridge fired in the chamber that makes it risky.

J E CUSTOM

 

[YZ-80]

The No Go gauge is used to tell you that the chamber is large or the lugs are set back to the point that the rifle "Should not be shot" because of possible case head separation that could render the weapon inoperable. It doesn't mean that it is unsafe. The military sets this dimension to prevent issues in the field that could cause the soldier to have problems that could be life threatening.
Normally if the bolt closes slightly on a no go gauge it will only be hard on cases and may eventually cause problems.

Head space can be more than the .006 and the fact that the brass cases are ductile means that for a few shots you may get away with it, but the magnums are a different story and many recommend holding it to .004 max.

If you have a rifle that a no go gauge will close on, you can do minimum sizing (Just enough to chamber) and brass life will improve because the cases are no longer SAMMI dimension but will work in that chamber and That is .006 thousandths longer than a SAMMI chamber. It isn't the size of the chamber, it's the size of the cartridge fired in the chamber that makes it risky.

J E CUSTOM

Thank you fine sir. I have a much clearer understanding of the concept now!