The M16A4 is lightweight, versatile, accurate, easily maintained rifle
It has a muzzle velocity of 2800 fps and a max effective range of 800 meters against an area target. It has a cyclic rate of 800 rounds per minute.
It weighs just 8.7 lbs (w/ 30 round magazine inserted)
The m14 is heavier and less easily maintained.
It has a muzzle velocity of 2800 fps and a max effective range of 460 meters. (Not talking about the scoped enhanced versions we use today). It has a cyclic rate of 750 rounds per minute.
It weighs in at 11 lbs with a 20 round magazine inserted.
The M1 Garand is also heavier and even more difficult to maintain than the M14.
It also has a muzzle velocity of 2800 fps and a maximum effective range of 440 yards.
It weighs in at 11.25 lbs w/ it's 8 round clip inserted.
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I don't know if the M16A4 would be admissible in this, because it wasn't first mass fielded until 2003, but if not, I would take the M16A2 over any other "stock" (ie - not match grade or anything) assault rifle that we have used in the 20th century.