Well then, the guys on you units firearms team needs some learning. Where did they get that "information" from?
They have it backwards. The projectile de-stabilizes after impact. When M855 ball is fired into flesh it will in 2-5" of penetration begin to tumble as I call it, guys who like big words will say yaw. At a velocity of 2700 fps or faster M855 ball will seperate at the point between the steel and lead core, causing fragmentation. The fragmentation velocity is gone at about 90 meters of travel and will still tumble in flesh but will not reliably fragment. When it hits flesh and tumbles and does not break apart it still makes for a nasty wound.
Even when I used M955 ball that has a hardened tungsten core that still has a air pocket will still tumble in flesh in 2-5" of penetration but will not fragment due to the hardness of the core. It worked spectacular up close when we had to shoot through cars that would destroty the M855 projectile. The M955 penetrated, and still "worked" with wicked reliability.............
I would like to talk to your firearms unit guys, they have it all backwards. I can give first hand experience on how the 5.56 works from contact to just over 200 meters.