What is the Tolerence of a 303 NO GO Gage

[albayo]

This question is for members about NO GO gages.

I am looking for information on the correct tolerance of a 303 British NO GO gage. Are there different thickness NO GO gages, meaning are there differences for military, and commercial tolerances?

I have a commercial NO GO gage that is marked .067 and I received one that was milled out (but not marked) as a spare measuring .0735 to .0755. This is depending on which side you use the Micrometer, as it is not uniform. Which one is closer to acceptable tolerances allowed for a 303, .067 or .075?

I have an electronic micrometer, and I zeroed it a number of times to be certain I had the correct measurements.

Your help would be greatly appreciated.

Thank You

Albayo

 

[guntech]

The military use three gauges.. go, no-go, and a field gauge.

Ideally the bolt will close on a go gauge and not close on a no go gauge.

If it does close on a no-go gauge it is still acceptable if it does not close on a field gauge.

I believe there is 6 thou difference between the gauges. I am not sure. I never use field gauges, I use go gauges and a piece of masking tape on them to make a no go gauge. It is a bit tighter than military specs that way.

 

[tiriaq]

Military GO is .064, NO GO (which is actually used more like a FIELD gauge) is .074. Civilian NO GO is .067, I believe. It would be useful when fitting up a rifle. I suspect a lot of servicable Lee Enfields would swallow a .067.

 

[albayo]

Gages

Thank you gentlemen.
I wasn't sure if I missed some information or there was some sort of mistake in the second gage. I haven't found a P14 that wouldn't swallow a .067. So the second gage .075 could be used as a field gage.

Albayo

 

[woodchopper]

0.074" is military field guage

Most enfields will swallow a 0.067" gauge.

I checked all my enfields one day and no surprises most would easily close on the 0.067 and 2 were over the 0.074, luck has it they were both No4's with 0 bolt heads so that was an easy fix.

 

[sunray]

"...it is not uniform..." You're measuring what would be the rim aren't you? If there's any non-uniformity on the rim part, pitch the guage. It's not giving you an accurate test of the tolerance. Headspace being nothing more than a manufacturing tolerance. The guages don't measure anything. Nor is there much of a tolerance in the size of the guages. Maybe +/- 1/10,000". Guages are precisely made instruments that are turned to size, heat treated and precisely ground to a finished size.

 

[speerchucker30x378]

Head space is always one of those things that gets blown totally out of proportion in the gun industry. Hatcher actually increased the head space in a 30-06 by .040 of an inch over the specs and observed no ill effects. Its more of a standard to make sure that Remington’s ammo will fit in Browning’s rifles and Weatherby’s ammo will fit in Remington’s guns and so on ;o)

 

[guntech]

Head space is always one of those things that gets blown totally out of proportion in the gun industry. Hatcher actually increased the head space in a 30-06 by .040 of an inch over the specs and observed no ill effects. Its more of a standard to make sure that Remington’s ammo will fit in Browning’s rifles and Weatherby’s ammo will fit in Remington’s guns and so on ;o)

That's a relief to hear... now all us gunsmiths can relax... For 40 years I have been setting the headspace so you can just close on a go gauge... I'll have to ask the next barreling customer if he would like to try one with 40 thou excessive headspace.

 

[speerchucker30x378]

Well I figure over the last 25 years I have installed over 700 barrels and I must admit that I head space the same way you do. But the point remains that there is no reason to get all out of joint and in a tizzy just because you old mauser has gained .004 head space over the years most old mausers are only worth $70 so I can see no point in setting the barrel back and re-cutting the chamber. Shoot it the way it is )

 

[woodchopper]

That's a relief to hear... now all us gunsmiths can relax... For 40 years I have been setting the headspace so you can just close on a go gauge... I'll have to ask the next barreling customer if he would like to try one with 40 thou excessive headspace.

and I was thinking of sending you a project in the spring