Something else that struck me when looking at the chart in the...

Something else that struck me when looking at the chart in the link below comparing penetration into 3/8" steel plate you will see that the M855A1 has more than twice the effective range for penetration compared with the M855, I initially thought the steel/copper sleeved projectile would have been lighter than the lead/copper one , but I read that is not the case, therefore if both projectiles are the same weight then the M855A1 must be travelling at more than twice the velocity of the M855.

That relates to E=MC squared

http://bulletin.accurateshooter.com/2010/06/u-s-army-issues-new-m855a1-ammo-to-troops-in-afghanistan/