it was a m21, a slightly modified m14, not a m1, I believe. The m21 front sight has been milled thinner to make 300 meter head shots, glass bedded, trigger worked, and there's a mod to the cycling system. And it's topped with a Art 1 or 2 scope, that can be removed. The Art 1 scope had a harder cam screw and stayed accurate longer. As far as I can remember. FT. Campbell/101st Abn Asslt still fielded the m21 in the late 80's. And had its own sniper school to use them taught by a Joseph White, and asst Mr Boswell. Both VN 5 grp guys, Mr White had 73 confirmed, coached Olympic team, Presidents 100 as well, and his favorite saying was "Dont worry your Air Assault, you can run 4 miles,,,, but cant shoot worth a ****". Mr. White was the best shot I ever saw. Watched him with a struggling students m21 with iron sights(Art 1 scope removed)at 600 meters shoot a shot, had it marked with a spotter and then put 6 more rds into that spotter with the last round shooting the spindle out and the spotter fell. A sub 6" group at 600 meters, with irons, student couldn't blame the rifle anymore. Unbelievable, but I witnessed it.
I relay this info because I cut my teeth with a 308, and worshipped it. But here's the rub.
Imo the 308 caliber needs a 300 wm case to push it effectively at a minimum, to be effective LR round.
A effective LR round needs a g1 bc of .6 and a case with enough powder to push it at 2900+ fps, by today's standards, imo.
The 308 win is a good intermediate range cartridge. You can shoot out past 800 with a 308 win but wind drift on .5ish g1 bc bullets make variable wind hits hard, and not certain. BC is everything in LR. The 308 win is not a efficient enough round with the modern equipment of today. Will it work yeah, but there's better, imo.
And for hunting one should use a ballistic app and see if a round has the minimum energy desired at whatever max range you want to hunt. Bullet manufacturers recommend (X) amount of speed for bullets to work, usually ~1800 fps minimum or about 1200 #'s. So look at the 308 win numbers, it's an intermediate range round. Imo the 7 rem mag is the smallest effective LR round with the energy to kill effectively as well.
edit- yes theres a few other cartridges in that light mag category like the 280 ai or 270 wsm with just enough energy, but you get my drift.