A friend broought me a rifle for evaluation. The action was a Gew.98, but it had evidently been "sporterized" in Germany in the 1930's, since it bore a proof mark from that era. He told me that it was ostensibly a 7X57, and cartridges of that caliber would chamber and fire, but that his local gunsmith had told him that it had excess headspace.

Among my tools are a collection of chambering reamers and headspace gauges I inherited from my late gunsmith friend, Harry Creighton. I could find no 7X57 gauges among them, but did find three gauges marked ".244 Remington". One was marked "Go", another "NoGo" and the third was unmarked. I assumed the last was a "field gauge". All three of the gauges chambered in the rifle with no resistance.

I concluded that the gunsmith was correct, but that left unanswered the question as to whether the rifle was safe to fire. I had a box of factory ammunition, but no gauge, like a Wilson gauge, which would measure the headspace of a fired cartridge.

I decided to use the seating die of my 7X57 die set as a makeshift headspace gauge. I removed the bullet seating plunger and inserted a factory cartridge into the die. I then measured the protrusion of the case from the die using a vernier caliper.

Next I test fired a factory cartridge in the rifle, holding it at hip level and pointing it in a safe direction down range. I inspected the case and determined that the primer was not flattened and did not protrude from the case head. Finally, I inserted the fired case in the seating die and measured the protrusion, again using the vernier caliper. The difference in the measurement between the unfired cartridge and the fired case was .005", as close as I could determine.

Given the fact that factory ammunition is not manufactured to maximum dimensions, I concluded that the excess headspace problem was minimal and that the rifle was safe to fire. However, I suggested that rechambering the rifle to .284 Winchester or 7X64 were options which would clear up the headspace problem.

1. Was my method an effective way of measuring excess headspace?

2. Was the rifle, in fact, safe to fire?

3. Was my rechambering suggestion correct?

Yikes, not another headspace issue.
The German Gewehr was never made in 7mm, so right there is one thing, so it has been rebarreled.
You proved it was safe to fire. Why bother to rechamber?
Your test does not account for any case stretch so is invalid. Better to use a shim on a case head, or on one of your gauges to see where you are.
As has been said a million times here, just make the brass fit the chamber and drive on.