What's the maximum practical range for an iron sighted double, shooting off a bipod or tripod, at plains game?

I have made several 1-shot kills on African antelope in excess of 200 yards with a .300 magnum. A double is not as accurate because of (a) no scope sight (at least as I would use it), (b) regulation, and (c) trajectory.

Regarding iron sights, I can easily hit game-sized targets at 200 or 300 yards. However, that's using aperture sights and a black bull on a contrasting white background, and at a known range. Field conditions and open sights are harder.

Can double sights even be adjusted finely for elevation?

Regarding trajectory, I have a .458 bolt rifle. Sighted at 100 yards, it is about 6 or 7 inches low at 200. I imagine a 9.3x74R would be a little better but a .450/400 worse, due to velocities.

All things considered, I'd guess 150 or 175 yards would be a tough shot, though I have no experience with doubles.

I once shot a caribou at about 250 with my merkel 8x57. everything else I ever shot with a double has been 150 or less.

I was stalking an eland once with my .458 bolt rifle but the shot was at about 150 and I switched from the iron sighted bolt gun to a 9.3x74 double because it had a scope on claw mounts and the bull was hard to see through the brush even though I had a clear shot.

I hope N.E. 450#2 post here. I know he has taken game at or over 300 yards.

My Sodia .338 is my most accurate double rifle. I've never needed to take a long shot with it but if I knew I would ever be in a situation where I would need to rely on a double rifle for a long shot the Sodia would be the one.