>>63865790
Projectile matters more than caliber. 77gr OTM is good, but other 5.56 loadings are shit- especially 62gr green tip. 55gr M193 doesn't maintain enough momentum out of shorter barrels that are popular now.

>>63849873
This is only because those 7.62x39 wounds were caused by dinosaur M43 ammo or the Chinese equivalent that is known to be shit (just like 5.56 M855). Ammo selection matters way more than caliber itself.