More information at the firearmblog.com. Apparently it originally used a tin-bismuth core instead of a solid copper core.

In this post on accuratehooter.com blog, there is some information about the wunder powder in the comments.

Both this and the Mk318mod0 round seem to push the 5.56 case to the limits, far beyond what we reloaders would consider prudent. Then again, the military isn't interested in reloading :-)

Having seen what a solid copper Barnes TSX can do, I have no doubt this cartridge would be devastating.

I thought they already had a non-lead (tungsten?) ammunition issued?

I believe the ammuition industry has already worked out most of the bugs with the copper ammo (e.g. Barnes), so I expect the 5.56 rounds will work well.

If I understand it correctly, the lead free is primarily for training, as the millions of rounds sent into the ground at some military ranges have leached into groundwater over time (it requires a specific chemistry in the ground, and doesn't appear to happen everywhere). However, given the penetration and punch of the copper ammo, it seems like it would be a good combat round as well.

The tungsten turned out to be a carcinogen that actually leached into groundwater even faster than lead. They bagged that program PDQ.

Phillip, I thought it a stupid idea myself born of the Fed's paranoia about lead but did not realize it had been cancelled.

Barnes all copper bullets ROCK.

Expensive as Hell. Takes all the fun out of varmint hunting here in CA Condor country.

Wasn't it just a few years ago they were compalining about the shortage of copper which was affecting the production of brass. I remember the price of wire and copper pipe went through the roof. So now they want copper bullets?