. The 6mm or .243 will kill deer size game effectively at 350yds. However your margin of error maybe less than say a 30/06/ Only because it will leave a bigger hole going out.
350...? I kill deer without issue at nearly twice that with good bullets in the 223. Headstamps don’t mean anything, bullet do. Want more damage- shoot different bullets. There are 6mm bullets that will make most gag at the wounds left at 600 yards.
As for distances on deer with 243s, it’s the same as someone else pointed out- minimum impact velocity. That combined with bullets designed to/do cause massive tissue destruction means animals die really quick.
As for me-
115gr DTAC- 597 and 620 yards
105gr Hornady HPBT and AMAX- multiple to 500.
105gr Berger- multiple to 500.
95NBT- more than a hundred between 300-427 yards.
Placement, bullet design, impact velocity.
