I suppose the 10th Marine Regiment--the Jarhead Cannon Cockers--don't actually call themselves "redlegs", but they train at Ft Sill Oklahoma at the Army's Field Artillery School, so they'd know the term.
Looks chaotic, but it ain't. I got to observe one of the artillery battalions from the Army's 2nd Infantry Division on a live fire once, they were test firing their brand new M109 Paladins. Since they were brand new out of the depot, they were using the looooooong lanyard, and going slow, not working in the shelter. Still pretty cool.