Source?
My source was a retired Soviet Army Colonel, Afghan war vet, teaching my NVP class (Soviet basic training for the High schoolers), as well as other Soviet/Russian active duty staff.
I've had Army instructors, armorers, and combat vets tell me that if you don't stagger the gaps in the gas rings, the M16 won't operate. So...ya know, take that for what it's worth.

If I need to accurately relieve a target at 300 yards, I will use a .308 with an optic. The .223 at 300 yards is for groundhogs.

