My dad, God rest his soul, told me once that gunnery school instructors advised the men to "open mouth and stand on tip toes" when firing the guns. I see the open-mouth advice - that, effectively, would cause aa 'valsalva manaeuver' which clears the inner eaar. Tip-toe? What am I missing?

If it were to spare heavy wear on the ears, the advice to him was in vain: Dad died stone deaf and largely without even minimal hearing for the last 10 years of his life.
Any takers on this tale?

Bests, Steve