You were 20 years before me (USMC Infantry 88-94). Apparently the following generations of M16’s were/are considerably more accurate then your days. Easy shooting of torso targets at 500 with iron sights, even with sloppy, loose “combat worn” rifles.

Alas, you missed all the fun of a bruised shoulder and cheekbone from the buttstock and the spotweld! Seriously though, by then you should have had the M16A2 and M855 ammo, a significant improvement over the M16A1 and M193 we had. In case we’re accused of thread creep, I should add that all M16’s (and M4/AR15’s) are not created equal and some are more suited for long range use than others.