There's about 1.4 million people on active duty in the whole of the US military. Out of those, there are 433,000 enlisted people in the Army. Ignoring the other branches, and officers in the army, and at $100k a pop, it would cost $43.3 billion to equip all of the enlisted army soldiers. That's a bit under 1% of the military's annual budget of ~$550 billion. (from wikipedia)

On a per-soldier level, the army spends in the neighborhood of $50k to train a new recruit, from enlistment to their first assigned post. (source) Not 100% sure what exactly this figure entails, but I am guessing it does not include equipment. Could be wrong.

Anyway, regardless of its effectiveness in saving lives, it seems unlikely that the army would want to ~triple the cost of a new recruit. I believe it was mentioned in the discussion for the AK47 vs. M16 video that the main reason we are still using the M16, even though better weapons have been developed, is that we already have a lot of M16s, and it's cheaper to make small changes to the existing design instead of buying new guns for everybody.

would it be possible to use this version if a diamond member fixed it?
http://www.boreme.com/boreme/funny-2007/sarah-silverman-mtv-p1.php

Reminds me of this: Heathrow airport prank