You can not own post-ban magazines unless you are a member of the military using them on active duty or a cop. Pre-ban magazines may be used on pre- and post-ban rifles. NY city may have local nutty laws.

To try and explain a little better.

The 1994 Ban deems an "Semi-Automatic Assault Weapon" (SAW's) as a firearm that can accept a detachable magazine [b]AND[/b] has at least two of the following features:

1) A flash hider
2) A bayonet lug
3) A collapsible or folding stock
4) A pistol grip that "conspicuously protrudes below the action"
5) A grenade launcher

There is no specific mention of magazine capacity in the definition of SAW's. There is however a ban on manufacturing NEW magazines for the general public that are more than 10 rounds. State and Local Laws may very.

A Post ban rifle has only one feature (the pistol grip) and a detachable mag. If you were to remove the pistol grip you could add a flash hider and be legal. Or I suppose you could weld the magazine into the lower and load it from the top if you popped off the upper. Then you could have all the "evil features" and still be legal as long as the magazine was not detachable.

Does that help?