The width of the front sight of a rifle is an issue much overlooked by the guys who shoot nothing but scoped rifles.
Front sight on an M-1 Garand, for example, subtends 4MOA. It covers 4 inches of target at 100 yards, FORTY inches at 1,000.
That gallon milk jug is perhaps a sixth of that width.
Playing with a 7.62 Number 4 with PH sights one afternoon, I was happy enough to put 5 into 2-1/2 inches at 300, using DA 61 ammo, and twice as happy when my handloads came up to the standard. This was on the open range at Wolverine, standard gusting Manitoba crosswind provided free of charge.
IIRC the targets we used to shoot at long range in the DCRA game called for a 24-inch bull at 1000.
That is plenty small ENOUGH with iron sights at better than half a mile.
I invite all the guys who "know everything" to give it a try some time.