Measure it if you have one

[avidflyer]

Going to be a hard to measure to any super exact number, but I think I have a off spec (bad) 308 go gauge. Should datum on the 308 is .400 so if you have a crisp head space gauage see what you come up with. We made one on the lathe and used 2 hornady gauges and got these numbers. I did notice on the Whidden bump gauge it has a huge radius on the in side so it was worthless to use for a true 400 datum point. just an fyi...not that it wont work for a bump gauge.



Hornady gauge: Go: 1.6225, No Go: 1.6275
Hornady gauge: Go: 1.6230, No Go: 1.6280
ho-made gauge: Go: 1.6240, No Go: 1.6285

All were done with a dial caliper since I had no micrometer with sufficient range.

 

[Keith Glasscock]

My Go gauge measures 1.623 with a Hornady tool. It is marked 1.630.

I suspect the Hornady tool is the problem.

 

[Dans40X]

AND the industry standard for a caliper....IS?

 

[hoz53]

Going to be a hard to measure to any super exact number, but I think I have a off spec (bad) 308 go gauge. Should datum on the 308 is .400 so if you have a crisp head space gauage see what you come up with. We made one on the lathe and used 2 hornady gauges and got these numbers. I did notice on the Whidden bump gauge it has a huge radius on the in side so it was worthless to use for a true 400 datum point. just an fyi...not that it wont work for a bump gauge.



Hornady gauge: Go: 1.6225, No Go: 1.6275
Hornady gauge: Go: 1.6230, No Go: 1.6280
ho-made gauge: Go: 1.6240, No Go: 1.6285

All were done with a dial caliper since I had no micrometer with sufficient range.

These bump gauges we use are just for reference. To do what you're trying to do I would use the same gauge. My gauge won't be the exact same as yours and any numbers I would give to you would be meaningless.

 

[avidflyer]

My Go gauge measures 1.623 with a Hornady tool. It is marked 1.630.

I suspect the Hornady tool is the problem.

Thanks Keith

 

[avidflyer]

These bump gauges we use are just for reference. To do what you're trying to do I would use the same gauge. My gauge won't be the exact same as yours and any numbers I would give to you would be meaningless.

Agree gauges need to be the same to measure on the same 400 datum but Reference is what I'm looking for....we have chambered 3 or 4 barrels with these gauges, we get a new chambered barrel in and check it with these gauges....it closes on a no go...very popular smith, very good reputation, decades in business....so are our gauges or his gauges incorrect. They also came from a company that was plagued with problems for a couple years. One wouldn't think they would have 7 -12K difference

 

[DRNewcomb]

....ho-made gauge: Go: 1.6240, No Go: 1.6285....

You know a ho that makes gauges? That's handy.

 

[gotcha]

I don't know if this is possible at this time. But, a case fired in your chamber should match your go-gauge. I had a similar concern w/ a go-gauge and returned it to the Mfg. and had the measurement CERTIFIED in writing with an optical comparator .......... The go-gauge was accurately marked ... the problem was with the measurement method on my part........... You can't verify a H/S gauge with a Hornady comparator. In my situation I couldn't get a 6.5X47L F/L die to bump the shoulder enough to chamber a cartridge. Didn't know if it was the fault of the H/S gauge or the F/L die. I ended up milling .003" off the shell holder.

 

[memilanuk]

This is a long-standing 'issue' with the Hornady gauge... and the Stoney Point design before it. The holes may start out the correct size, but they are radiused, which makes it pretty much impossible to get them reading *exactly* 1.630" on a GO gauge, unless they were to sit there and test fit, machine a little off, test fit again, tweak it a little more...

These are mass produced items. As long as you treat the readings as *relative* to your chamber, not absolute, you'll be fine. It really doesn't matter (for the intent of this tool) whether your calipers read 1.623 or 1.630" on a GO gauge. What you're looking for is a relative increase or decrease i.e. a fired case is n thou longer than a virgin case, or a sized case is n thou shorter than a fired case. If you want to know how that stacks up relative to SAAMI case dimensions, get an actual set of GO/NO-GO gauges, and zero your calipers on those. In my scenario, my Stoney Point comparators measure 1.624 and 1.628 on the GO and NO-GO gauges respectively - exactly 0.004" apart, just like they should be.

It's really not that big of a deal.

 

[avidflyer]

This is a long-standing 'issue' with the Hornady gauge... and the Stoney Point design before it. The holes may start out the correct size, but they are radiused, which makes it pretty much impossible to get them reading *exactly* 1.630" on a GO gauge, unless they were to sit there and test fit, machine a little off, test fit again, tweak it a little more...

These are mass produced items. As long as you treat the readings as *relative* to your chamber, not absolute, you'll be fine. It really doesn't matter (for the intent of this tool) whether your calipers read 1.623 or 1.630" on a GO gauge. What you're looking for is a relative increase or decrease i.e. a fired case is n thou longer than a virgin case, or a sized case is n thou shorter than a fired case. If you want to know how that stacks up relative to SAAMI case dimensions, get an actual set of GO/NO-GO gauges, and zero your calipers on those. In my scenario, my Stoney Point comparators measure 1.624 and 1.628 on the GO and NO-GO gauges respectively - exactly 0.004" apart, just like they should be.

It's really not that big of a deal.

That's why we turned one on the lathe also, to ensure the 400 datum was crisp and not wore.

 

[avidflyer]

I could be wrong but I think the masses are thinking this is for brass sizing / bumping brass. Not worried about that I need it to be correct for chamber work. if the gauges are off by that much then my work is off that much. Hints the original problem between my work and the other smiths

 

[John Russell]

I don't know if this is possible at this time. But, a case fired in your chamber should match your go-gauge.

That would be nice, but it is wishful thinking. 98% of the time, they do not.

SAAMI Case can be from 1.627" to 1.634"
SAAMI Chamber can be from 1.1630" to 1.640"

A case takes a hellova lot of firing before it completely fills the chamber.

 

[Ggmac]

I'm sorry I don't understand . Your worried about tolerance while measuring without a micrometer and you do smithing ? Something is a little off or I'm completely missing the boat .
All gauges have + and - tolerances and your using less than ideal measuring protocol .

 

[avidflyer]

I'm sorry I don't understand . Your worried about tolerance while measuring without a micrometer and you do smithing ? Something is a little off or I'm completely missing the boat .
All gauges have + and - tolerances and your using less than ideal measuring protocol .

 

[avidflyer]

yes completely off It was a general question that half don't understand and the other half want to over analyze. I understand tolerance stacking and built in error. Over the last couple years ive sent about 1/3 of my tooling from a certain company back and think these gauges are crap. Just wanted some general measurements on what others had before I send them back and they take 2 to 3 months to resolve. Or have to order another set....

 

[Ggmac]

Oh , ok I think I understand . But realize Saami has a USUAL .003 between go and no go .
I use , dang I forgot his name , anyway , it's for cartridge datum line comp , I'll finish this a little later , I broke a few bones and am in a lot of pain and , well can't think too well .
Gary

 

[hoz53]

yes completely off It was a general question that half don't understand and the other half want to over analyze. I understand tolerance stacking and built in error. Over the last couple years ive sent about 1/3 of my tooling from a certain company back and think these gauges are crap. Just wanted some general measurements on what others had before I send them back and they take 2 to 3 months to resolve. Or have to order another set....

Well you probably know that some headspace gauges are different between different manufacturers. I understand you want to know why barrels chambered by your smith will close on your nogo gauge. I see what you're trying to do I just think there's to many differences and you wouldn't get meaningful info from anybody. I would buy a new gauge. Cheap insurance if youve buying that many barrels/chamber jobs.

 

[gotcha]

That would be nice, but it is wishful thinking. 98% of the time, they do not.

SAAMI Case can be from 1.627" to 1.634"
SAAMI Chamber can be from 1.1630" to 1.640"

A case takes a hellova lot of firing before it completely fills the chamber.

Been "at it" all day long so a little late answering. ....... Glad you said 98% of the time and you make a good point. However, with a min. spec. chamber I've had no problem getting complete F/F on 2nd firing. Alloy of particular brass and tightness of chamber vs. unfired cartridge size as well as heat of load & other factors determine the number of times a case needs to be fired to achieve max H/S length ................. Not wishful thinking IMHO ............. BTW how much is "hellova lot"

 

[Zero333]

My 308 go gauge measures 1.619" with the Hornyday comparator. A year ago it measured 1.620" with the same comparator. 2 years ago it was 1.6215"... The comparator bushing gets worn out, hence the shrinkage.