Once again different rounds for the Army and Marines is discussed.

via Military.com

The M855A1 features a steel penetrator on top of a solid copper slug, making it is more dependable than the current M855, Army officials have maintained. It delivers consistent performance at all distances and performed better than the current-issue 7.62mm round against hardened steel targets in testing. It penetrated 3/8s-inch-thick steel at ranges approaching 400 meters, tripling the performance of the M855, Army officials said.
The Corps had planned to field the Army's M855A1 until the program suffered a major setback in August 2009, when testing revealed that some of the bullets did not follow their trajectory or intended flight path.
The earlier design of the M855A1 featured a bismuth-tin slug which proved to be sensitive to heat, prompting Marine officials to stick with the M855 and also the Special Operations Science and Technology round developed by U.S. Special Operations Command instead.
Commonly known as SOST ammo, the bullet isn't environmentally friendly, but it offered the Corps a more effective bullet, Marine officials have said.

I'm going to have to get ahold of the testimony on this one but the Army's position seems indefensible.  They are sacrificing accuracy and maintaining that its an acceptable tradeoff.

That's not good.

Its probably a non-issue though.  The emphasis on infantry skills seems to be a thing of the past.  Adoption of the Army round is probably already in the cards....plus the M855A1 will more easily be declared armor piercing so banning it from public purchase will be easier.

Sidenote:  Lets not forget that Sanchez is a serious anti-gun zealot.  Her questions on this subject ARE part of an agenda.