What about this modification?

http://en.wikipedia.org/wiki/HK416

Some SF groups already use the 416 uppers as a rule of thumb, and I certainly don't blame them.

Subman, currently th army is using a 1:10 twist (this overstabilizes the round) so the fragmentation effect is only good when you engage targets under 100 meters. If the army went with a 1:12 twist as the M16 was designed for, then fragmentation distance could be sustained for a much longer distance, but that comes with the significant reduction of armor penetration.

So the pentagon decided to go with better armor penetration than fragmentaion on soft targets. However, I believe a reversal of combat strategy would be necessary as the enemies we're fighting have no regard for their lives or of the lives of those around them. The theory of taking our 3 men and clogging up the enemy's logistics with wounding tactics only works against organized and disciplined armies, but it doesn't work here. But hey, it's only my opinon (not that it makes much difference).