.303 Marked Gauge Tool... identity?

[Son]

Dear brains trust... these pics of a tool clearly marked .303 Case have turned up on another board... Can anyone tell me what it is for so I can end the agony we are going through there.... The was another post from the OP to show a case does not go over the long rod.,.. unsure if it was a new case or a fired case, waiting for an answer to that.... here are the pics... thanks in advance, gents

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Update to add... this description just got posted there...." it's a gauging tool in the manufacturing process cases before they are drawn out and tapered"

The case in the pic below is a fired, unsized case, so max size... The explanation makes sense... measure the web- periodic testing during a batch lot for setting tooling?

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Information

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[browningautorifle]

Makes sense, to determine the thickness at the primer pocket.

[mhb]

the spindle of which would contact the primer, it seems likely that it is intended to check primer seating depth. It is my understanding that British military ammunition which was loaded with Cordite was necked after the charge was inserted, so that it would have been primed while still un-necked, and the pictured tool seems suited to such a condition.
Alternatively, if the micrometer spindle nose is wider than the primer (can't tell from the photo, though the fact that it is tapered rather than straight makes this less likely), the device may be intended to check the thickness of the case head web.

mhb - MIke

[browningautorifle]

military ammunition which was loaded with Cordite was necked after the charge was inserted

That's correct.

the micrometer spindle nose is tapered rather than straight

Pic one shows a taper that I believe fits inside the primer pocket. Otherwise I think it would be square.

t it would have been primed while still un-necked, and the pictured tool seems suited to such a condition.

But this could be used as easily before priming, after the final draw.

[mhb]

at the head of the device appears (from the visible markings) to be a true micrometer, apparently American-made by the L. S. Starrett company of Athol, Mass.; measuring to the thousandth of an inch.
I did refer to the (apparent) recess in the nose of the spindle in an earlier post, and mentioned its possible relation to measurement of Berdan-anvilled cases.
There do appear to be other markings engraved on the body of the device, which, if deciphered, might well help solve the mystery...

mhb - MIke

[mhb]

The nose of the micrometer spindle does appear to be tapered, and there may be a recess in its point, which could serve as clearance over the Berdan primer pocket's integral anvil. The tool might be intended to check primer pocket depth, if the dimensions and taper of the spindle nose are appropriate, but without dimensions, it's still a guess.
As a measuring device, it appears best suited to measuring the thickness of the web at the head of the case, and, perhaps, at the bottom of the primer pocket (spindle nose dimensions permitting), since the support post would bear on the inside bottom of the case itself, and the tip of the post is the only fixed reference surface on the tool.
It would seem that a tool intended to measure the thickness of the case head web should bear more broadly on the base of the case, while one for measurement of primer seating depth would better support the case with its base against a reference surface.
Perhaps someone will know what it actually is, or come-up with a better guess.

mhb - MIke

[browningautorifle]

there may be a recess in its point, which could serve as clearance over the Berdan primer pocket's integral anvil.

That never even occurred to me, I was considering it for boxer primed cases...

[Son]

I think it is not likely to be to measure primer pocket depth as there is no datum to measure from- surely to measure the depth of the primer pocket it would need to be measured from the outside of the base in, so an ordinary depth micrometer would do that.

As it takes a measurement between the inside of the case head and the bottom of the primer pocket, I still think web thickness is it's purpose....

No more clues on the other board... will update if there is any. Thanks so far, guys.

[mhb]

would be the actual dimensions of the nose of the micrometer spindle. If, as appears likely, the tool is intended to measure the thickness of the web at the bottom of the primer pocket, why would the spindle nose be tapered? A cylindrical nose of just-smaller diameter than the I.D. of the primer pocket would certainly work as well for the purpose, and the taper (depending on the actual dimensions) might interfere by contacting the edge of the pocket before bottoming - though it is not really possible to determine from the photos, the tapered spindle nose appears to be too large to enter the primer pocket to full depth.
An ordinary depth micrometer would likely need a specialized spindle to clear the Berdan anvil in the center of the primer pocket.
Still puzzling...

mhb - MIke

[CINDERS]

#8 MHB if you look closely at pic #3 you will just be able to see there is a counter sunk hole in the end of the spindle that would allow it to go over the anvil.
Or further more perhaps it is for measuring the top of the anvil as opposed to the base of the cartridge as if it was to deep would allow the primer to sit a bit deeper which hopefully would still allow ignition but if the anvil was to high then the primer may not sit below the base of the cartridge or worse still proud causing all sorts of issues not only in the field but in production.
That's my take on it.