Earplugs...
I too am enjoying the R. Lee Ermey shows re. various weapons and their histories.
IMHO, it would be nice if the owner of the weapon, the one who paid for it and has maintained it in pristine shape, were the one who gets to fire it on TV, but, well, Ermey is the star and he gets to BE the star.
That said, otherwise the show is both entertaining and educational, and I appreciate both. Have seen the artillery, tanks, and machine guns shows, and have the pistols show recorded. Will catch it when I have time.
Machine guns: Wish the show had included Da Vinci's multi-bbl cannon--a dozen small bbls (maybe .50 cal.) side by side, on a rotating rack with 3 such racks--one rack to fire, one rack cooling, one rack being reloaded. Gee whiz--he went back to Da Vinci's tank! Also would have liked to see the "potato digger" machine gun in action. Ah, well, you can only get so much into an hour show, and what they did show was darn nice.
Re: the earplugs: There is a style of earplug, which has a plastic inner end that goes into the ear canal, and a metal outer end that protrudes from the ear just a small distance. No experience with these (I favor muffs, myself) but they are a HECK of a lot more effective than .45 empties. I think this type of plug is what The Gunny is wearing.