After sighting in the irons at 100 on my FN SCAR-17, I bumped the BDC dial to 300 and fired a careful 5 shot group at the 300 yard line, from a bench, using a bipod. I was shocked to find a 3.5" group downrange with only MagTech M80 Ball ammo !
And of course you've done it multiple times with a WWII surplus M1 Carbine, since that's what we're talking about here.