[RebelBanker]

Standard load of two full pouches and a full magazine in the rifle:
M-14 - 2 x 20-round mags per pouch and 1 in the piece = 100 rounds
M-16 - 3 x 30-round mags per pouch and 1 in the piece = 210 rounds

The lighter 5.56mm round was adopted for "spray and pray" jungle warfare where the ranges of the firefights was expected to be very close and volume of fire was more important than maximum range.

Also, a loaded M-14 weighs over 12 pounds, an M-16 about 7 1/2.

[Natural Law]

Since the time of Alexander a grunt will carry as much as a grunt can carry. Roman soldiers were called Marius' Mules because of the amount of equipment each had to carry. The British Brown Bess weighed 14 lbs without the bayonet. Modern soldiers are no different. Most fire fights these days are not sustained events with significant movement and maneuver. More often than not the command "drop your packs, weapons and ammo only" preceded and excitement.

[Who is John Galt?]

...a loaded M-14 weighs over 12 pounds, an M-16 about 7 1/2.

Actually (according to the US Army), the current M-16 runs 8.8 pounds, including a sling and a loaded 30-rd magazine. And while the M-16 has been putting on the pounds over the years, the FAL has been dropping them. My favorite FAL (and it's one I built myself, not an exotic toy ;>) weighs in at about 10 pounds even (including the sling & a loaded 20-rd mag).

For a difference of about 19 ounces, I would personally take the 7.62 FAL over the 5.56 M-16 any day (but that's just my opinion)...

;>)