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Dutchman's pattern seems to be more axed on the CIP side of a headspace gauge.

SAAMI have different ways to check the headspace, but it is not as precise as the CIP way;

Many times you take headspace (with US go/ field / no-go gauge) on typical CIP calibers, let's say a 8X57 IS and/ or a 6.5X55 SE that will show "advanced field" or even no-go.

Because CIp takes in count more datas, it makes it more precise and if you check the same firearms with CIP standards, they will pass the test easily.

For that reason, I must say I like Dutchman's way of doing things.
 

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CIP standard gauges are;

BR/1 - General shape
BR/2 - Lenght L3 - Dia H2
BR/3 - Shoulder cone - L1/P2, L2/H1

etc, etc, etc...... and goes on .....

From CIP Annex 1, rev. 00-06-06

Maybe should you get a CIP standard book.... It is way more precise than any SAAMI standards....

If the gauge only means to measure the flange headspace, I agree, but to proper check a chamber, nothing comes to the heel of the CIP standard gauges.... On such old guns (and "obscured ammos) everyone should proceed a chamber cast. There is no gain in not doing so.
 

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The way I saw it was that Dutchman wanted to make it an complete specs gauge, wich is quite looking like his drawing.
Such a gauge makes a check on every important dimensions at once.
Dutchman, if you have access to a lathe, you should make your gauge with the tolerances from the CIP. It is quite easy to adapt since it is not made for only one caliber, but standardized with + - tolerances.
 

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Andy,

My first choice goes for a chamber cast!. But regarding the use of headspace gauge, for such "obscure" calibers and "unknown" or "in the dark" chamber condition, I do really prefer, and it's my own personal choice, to use at least, a shoulder locating gauge together with the rim headspace gauge. On pre-1920 (about that, it's not sutck in concrete and also depends on who was the manufacturer) the chambers are often longer than what they should, and base diameter is, quite often bigger than what it should be. This comes from my personal experience of older firearms, and you'll never see me shooting such a firearm before a chamber cast....

Regarding the pressure, since it's very hard to get the truth regarding pressure, we can only speculate about that. Pressure is not a simple thing in a gun; it depends on bore diameter, throat lenght, chamber measurement etc.... If let's say Norma says their loads are at XXXX bar (or PSI) they already added (generally 15%) extra to their data. So, you should never base your load on the velocity they announce; 1500 fps in their test rifle for XXXX pressure might be the same as 1275 fps in yours... for the same pressure. Also, and it's a personal choice, that's why I genrally keep my reloads, for older guns at no more than 85% of the maximum announced load, even if no pressure signs are presents.
 
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