Could you use a new unfired brass as a go gauge, and same brass with tape to act as No go?
Yes, It can be done. You question starts with "Can you...?" I have, I can and I will. Before the Internet using a case to measure the length of the chamber from the shoulder of the chamber to the bolt face was an option, in the old days a smith used rational as in why they choose one way over another, today in is more about insult through innuendo.
I do not know if reloaders on this forum can bump the shoulder back .001", or .002", I know they claim they can.
Question: If a reloader can adjust the die in the press to bump the shoulder .001". why cant they adjust the die in the press to move the shoulder back .005", or .006" or .010"? The reloaders world revolves around moving the shoulder back, why? If anyone knew we would not be having this conversation.
I purchase cases fired in trashy old chambers. chambers that are no go-gage length to filed reject length from the shoulder to the head of the case. I form cases to fit a chamber. 'WHY?' The go-gage that is coveted by reloaders and smiths will fit and allow the bolt to close every time the bolt is closed on it, then? after the bolt is closed the reloader still does not know the length of the chamber. That puts me so far ahead of most reloaders simply because I measure the length of the chamber from the shoulder to the bolt face in thousandths. Then there is that part about rational, why?
There is a correlation between the chamber and die, the die is adjustable, I transfer the measurement of the chamber to the die in the press. Bump? When the shoulder is bumped the case body increases in diameter, meaning it is not possible to bump the shoulder with out having case body support.
A reloader has one choice between .000 and .009" when determining the length of a 30/06 chamber. The one choice is .005" longer than a minimum length case, the go-gage can be used determine if the chamber is shorter than a go-gage length chamber but is will not indicate the length of the chamber in thousandths. The next choice beyond the go-gage is the no go-gage. the no go-gage is +.009" longer than a minimum length full-length sized case. Again, I have 4 choices between the go and no go gage. then there is the field reject gage. the field reject gage is .014" longer than a minimum length full length sized case and .009" longer than a go-gage.
But if a smith and or a reloader was talented they would not need but one gage, the go-gage, a gifted and talented smith and or reloader would be reading the length of the chamber from the shoulder to the bolt face in thousandths. They would benefit from if they had a good understanding of transfers and standards. I am the fan of transfers and standards.
A reloader can bump the shoulder back .001" but they can not figure how to move the shoulder forward without firing. Before I allow that small stuff to get the best of me I start with long cases like the 280 Remington. The 280 Remington case is longer than the 30/06 by .041", the shoulder on the 280 Remington is ahead of the 30/06 by .051", for those that can keep up, how can a reloader that understands case forming miss.
Then there is necking up, I did not/do not need 338/06 cases, I do not need 35 Whelen cases, but 'JIC' I always have 300 cases necked up to 35 Whelen and 338/06, never know when I will need cases sized to a chamber with an unknown length.
F. Guffey