And your avatar has a .30 carbine in it....

I'll admit that I was very biased against the M16A1 and it's varmint cartridge when I was first issued one. However, it grew on my over time. The M16A1 was light, very handy and plenty accurate out to 350 meters. And the original M193 cartridge was quite effective in term of wound ballistics out to its fragmentation range of about 200 meters and was still quite effective out to it's maximum tumbling range of about 250 meters.

The problem was that the US military decided that it needed the SS109 projectile in the M855 cartridge, to enable it to penetrate a steel pot at 500 yards - as simulated by a 10 gauge steel plate. M855 was successful in that it will do so out to nearly 600 yards compared to about 450 yards for M193, however the heavier 62 gr bullet reduced the muzzle velocity as well as the maximum fragmentation and tumbling distances with the round, compared to M193, which meant in an M16A2, the maximum fragmentation range was reduced to about 100 meters and the tumbling range was reduced to about 150 meters.

Worse, the military decided it needed the shorter 14.5" M4, which further reduced the velocity to the point that the M855 round will only fragment out to around 50 meters and tumble only out to around 95 meters.

And of course the US military complicated the issue by adopting a 1-7 twist barrel to accommodate the much longer M856 tracer round, when 1-9 twist was ideal for the M855 round, and 1-7 was too fast for accuracy with the 55 gr M193 round.