I salvaged a grain of naval gun propellant from a first word war wreck's 5" naval rifle. Its a cylinder about 1/2" in diameter & 1" long. It has not one but 6 small holes passing through it longtitudinally.
I was told they were there to regulate the burning rate by giving a bigger surface area exposed to combustion.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”