Carlos Hathcock and his spotter( Jim Land I think it was) once shot a VC scout to pieces before he stayed down for good. Later it was determined the VC was high as a kite from chewing betelnut. Been a while since I read the book but I seem to recall that it took 7 or 8? rounds to do the job. Hathcock was shooting a 30-06 Winchester M-70 and his spotter an M-14. No questioning the knock down power of those two rounds.
In the book Blackhawk Down the Delta operators were quite disgruntled about the performance of the then relatively new M-4 Carbine saying that more often than not the Somali insurgent would take 3-4 rounds through the chest before collapsing or turning to stagger away. Again it was evident the insurgents were high on something when hit and evidently the drugs were dulling the effects. I believe it. I once got into a slug fest at the local honky tonk with a rather large dude that was high on crack cocaine and just about got hung out to dry. No matter how hard or where I landed a punch they had little effect.