Nevermind, I'm just a doofus.

Timfoilhat

Timfoilhat

Time is my accomplice
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I have some factory new Norma brass. I ran it through my Forster full length sizing die and measured it with an RCBS tool I have that measures case length from base to the datum point on the shoulder. According to the spec for .308 Winchester that measurement is supposed to be minimum 1.6300. I'm measuring 1.6295 on the new sized brass. Is this a concern? Don't want to blow my face off so figured I'd ask before I assume.
 
thaifighter said:
Indulge my curiosity....

What is the published tolerance on the tool you are measuring with in ten-thousandths of an inch?

I think you will be ok with a high level of confidence...
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The tool is reported to be set to it's zero line at 1.6300. I regularly load and shoot stuff that measures 1.6298 and 1.6299. I just wanted to ask is the extra .003 of space is going to be a problem. Shooting from M1A.
 
beamernc said:
It's .0005" not .005", huge difference.
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I know this in my brain,but it seems like a lot when using the tool. It's like and extra 1/8 turn past zero where zero is minimum spec. Seeing it on paper like you just wrote gives me some perspective.
 
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I just remembered I have a set of Forster go/no-go gauges. I measured the go gauge that supposed to be 1.630. The tool say it's 1.629. I trust the Forster go gauge to be true before I trust the RCBS tool. This new detail means the brass is measuring 1.626 which is still .0001 too small. I'm thinking it doesn't matter, but I'm not an engineer and and I know that eventually the extra .001 does matter if it happens enough.

Edit...I lost a digit again. The tool is supposed to be 1.6300. It's actually measuring 1.6299 per the Forster go gauge. So my brass is measuring 1.6296. I'm well within spec. This makes more sense. Norma brass is supposed to be perfect, and here we've proven it is, and I'm a doofus. I'm changing the title to this thread now to Tim's a doofus.
 
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Buddy, pal, friend. Going down to the "ten thousandth of an inch" is wayyy beyond a concern for ammunition reloading. The finest of the fine brass manufacturer "may" be so specific that they pride themselves on one hundred of an inch uniformity.

Specific accuracy for all the variables of reloading for the highest level may get that deep in the weeds. But it's only plausible then.


Brass within a tenth is pretty well safe to shoot. At .0001 level of precision your going well beyond the standards(I e. the factory tolerance) of RCBS, Forster, Dillon, Wilson or any other commerical reloading tool maker.

I'd hazard a guess that such tolerances are beyond Brown and Sharps, Starrett, Mitutoyo, etc's standard offerings in the precision instrument world.

It's pretty awesome that you see it at that level. But I'm not sure it's a concern.
 
Timfoilhat said:
This new detail means the brass is measuring 1.626 which is still .0001 too small.
Click to expand...
"This new detail" confused me. How is the brass now measuring 1.626" when it was 1.6295"?

If you are comparing the min. dimension of 1.627" to 1.626", the difference is .001" not .0001".

3 decimal places is thousands, .000
4 decimal places is 10 thousands, .0000
 
Timfoilhat said:
I just remembered I have a set of Forster go/no-go gauges. I measured the go gauge that supposed to be 1.630. The tool say it's 1.629. I trust the Forster go gauge to be true before I trust the RCBS tool. This new detail means the brass is measuring 1.626 which is still .0001 too small. I'm thinking it doesn't matter, but I'm not an engineer and and I know that eventually the extra .001 does matter if it happens enough.

Edit...I lost a digit again. The tool is supposed to be 1.6300. It's actually measuring 1.6299 per the Forster go gauge. So my brass is measuring 1.6296. I'm well within spec. This makes more sense. Norma brass is supposed to be perfect, and here we've proven it is, and I'm a doofus. I'm changing the title to this thread now to Tim's a doofus.
Click to expand...
A lot of folks that don't deal with small dimensions like this get .001 and .0001 confused.

Like Trevillian said above, most "homeowner" measuring devices, are not accurate enough to measure to 4 decimal places, especially calipers.
 
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Trevillian said:
Buddy, pal, friend. Going down to the "ten thousandth of an inch" is wayyy beyond a concern for ammunition reloading. The finest of the fine brass manufacturer "may" be so specific that they pride themselves on one hundred of an inch uniformity.

Specific accuracy for all the variables of reloading for the highest level may get that deep in the weeds. But it's only plausible then.


Brass within a tenth is pretty well safe to shoot. At .0001 level of precision your going well beyond the standards(I e. the factory tolerance) of RCBS, Forster, Dillon, Wilson or any other commerical reloading tool maker.

I'd hazard a guess that such tolerances are beyond Brown and Sharps, Starrett, Mitutoyo, etc's standard offerings in the precision instrument world.

It's pretty awesome that you see it at that level. But I'm not sure it's a concern.
Click to expand...
My problem isn't that I wanted to go that precise. It's that the tool goes down to that .0001 level and all the specs are at the .001 level...and I keep forgetting the tool measures out the the fourth decimal.
 
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Timfoilhat said:
My problem isn't that I wanted to go that precise. It's that the tool goes down to that .0001 level and all the specs are at the .001 level...and I keep forgetting the tool measures out the the fourth decimal.
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I get that. "Safe to use" is in the .01/hundredths range. Arguably the .1 or tenths range. That is also the "cutoff" of general load data, even "precision" data. Going all the way to .001/ thousandth or as you are talking about .0001/hundred thousandth is getting well beyond anything cartridge related and getting into a whole world beyond our little hobby.
 
Trevillian said:
I get that. "Safe to use" is in the .01/hundredths range. Arguably the .1 or tenths range. That is also the "cutoff" of general load data, even "precision" data. Going all the way to .001/ thousandth or as you are talking about .0001/hundred thousandth is getting well beyond anything cartridge related and getting into a whole world beyond our little hobby.
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I get that. I use the tool not so much as a measure as I do a point of comparison. I can make sure I'm in spec with unknown/new brass by dropping a few pieces of the new stuff in there to make sure it's "about the same". This new brass was not the same.
Thanks for helping keep me grounded. I just needed to look at this and focus.
 
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Timfoilhat said:
My problem isn't that I wanted to go that precise. It's that the tool goes down to that .0001 level and all the specs are at the .001 level...and I keep forgetting the tool measures out the the fourth decimal.
Click to expand...
Significant digits are significant!
 
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