Hey Nomercy,
As far as the high capacity magazines go, you've always been able to use them with pre or post ban rifles, just as long as the magazine itself is preban. And any post ban high capacity magazine is illegal to use period, whether it's on a pre or post ban rifle. It's actually illegal to purchase them unless you're law enforcement.
As far as the rifles made between the ban, no one really knows. I myself have a DPMS A-15 Southpaw and contacted DPMS a few days ago, asking them if they'd add on preban parts to postban weapons after the ban. They said that they didn't know yet, and that they'd watch what congress said about the matter before doing anything.
P.S. I checked into the features of "assault weapons" and you are right. The technical classifaction of an "assault weapon," (at least until Monday) according to <
http://www.awbansunset.com/whatis.html> is that it can accept a detachable magazine and two or more of the following features: Folding or telescopic stock, Pistol grip protruding conspicuously beneath the stock, Bayonet mount, Flash suppressor or threaded barrel, and Grenade launcher. So a legal gun can only accept one or none of them and a detachable magazine.
Thanks for pointing that out. It's those kinds of mistakes that allow proponets of gun legislation to say gun owners don't have their facts straight.