How long ago? M16? M14? M1? or '03A3?
They still have 600 yard military rifle matches - not necessarily associated with the military, but the shooters use military rifles such as M-14, M-16, Garand, etc. My friend in Ohio has competed in this.
They use open sights, and IIRC, shoot at those distances from the prone position. I’ve shot 200 yard matches - we shot standing, kneeling, and prone.
How long ago?
“All ready on the left? All ready on the right? All ready on the firing line! Shooters, remove ramrods! With a paper cartridge and one round, load! Prime your musket!...”
For the tournaments they gave us M1 Match weapons. And yes I hit the target. We shoot from sunup to sundown. Rifles in the morning, pistols in the afternoon.