Pulled some duty working in the "target butts" on GI ranges. You know the ones you see in the movies? Target gets shot, then pulled down (out of sight), then raised back up, and a pole with a disc on the end is held up over the bullet strike (or waves across the target if you miss completely - look up "Maggie's drawers
), Did that. Bullets 6-8feet overhead. You hear them very clearly.
Kind of like rice Krispies. Snap, crackle pop. the crackle of distant rifle fire, the snap of the bullet as it goes by, the pop when it hits the (paper) target...
Also trained under live fire, machine gun fire at waist height, crawling underneath...and had the dubious pleasure of actually being under fire a time or two in my life.
The muzzle blast is a distant boom, arriving well after the rifle bullet. The crack can be heard for a long way too. If you hear a snap, or a pop, a thwip or a zip, its danger close (feet). If it sounds like a bumblebee the size of your hand, you are in a place you need to be gone from, RFN!!!! (inches)
Artillery is even more fun sounds. Quite distinctive. Been there, done that, too. had nervous 4th of July for several years after. Military service is such an educational opportunity is so many ways....