“...Like to see what a 7.62x39 would do.”
Less than a 5.56x45mm Ball M193 at all ranges inside 547 yds (55gr FMJ boat-tail at 4350 ft/sec muzzle velocity).
Peter G Kokalis, one of the foremost authorities on small arms field effectiveness, rated the M193 round as more effective than both 7.62x51mm NATO Ball M80 and US 30M2 Ball (WWII 30-06 round, tailored to M1 Garand), inside ranges of 109 yd. Traveling at much higher velocities, the 5.56mm bullet goes unstable on hitting the target, yaws and breaks up, expending a greater amount of its energy inside the target. The 7.62mm and 30 cal rounds simply punch through.
Outside 109 yd, the situation reverses.
“...55gr FMJ boat-tail at 4350 ft/sec muzzle velocity ...”
Confound all typos.
“4350” should read “3250”: roughly 1000 m/sec.