The Brits called them "Charge bags", they were once silk so they'd burn completely. IIRC they came in different weights, a #1, a #2, & a #3. You could calculate a formula for range by mix n' matching the bags.
The Brits used cordite, but the U. S. navy had some kind of granular powder like I described.
"Known as SPD, this new propellant was first produced in 1908 and adopted as the standard propellant formulation by 1912. SPD was found to have good stability characteristics when properly stored, with some lots manufactured prior to World War I staying in storage for as long as twelve years without loss of stability."
It was ignited by a 30-40 Krag blank inserted seperately into the breech of the rifle.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”