this is the best definition of the ban i have read, it is from
http://jpar15.com/customer.htm
On 9/14/94 we were advised by the Bureau of Alcohol, Tobacco & Firearms
that the Crime Bill does not allow any lower receiver to be completed into
an "assault rifle" as it is defined in the Bill. It does not matter when the
lower receiver was manufactured, only when it was assembled as part of
a complete rifle. In other words, you cannot buy a so-called "pre-ban
lower" and assemble it into a rifle that meets the definition of an "assault
rifle" as described in the Crime Bill.
After September 14, 1994, no lower receiver can be completed to form a
"semi-automatic" rifle that has an ability to accept a detachable
magazine and has two or more of the following features:
A.a pistol grip that protrudes conspicuously beneath
the action of the weapon
B.a flash suppressor or threaded barrel designed to
accommodate a flash suppressor (a recoil reducing
device is considered acceptable)
C.a folding or telescoping stock
D.a bayonet mount
E.a grenade launcher
What this means is that you may have a post ban ("post ban" meaning
assembled after 9/14/94) AR-15 rifle which has only one of the listed
features, and that is the pistol grip. It was previously believed by most
people in the industry that "thumb-hole" configuration stocks were a way
to technically eliminate the "pistol grip" feature on a rifle. However, BATF
has now interpreted the Crime Bill in such a way that it isn't possible to
construct an AR-15 type rifle without a pistol grip regardless of the stock
configuration. Because there is no way to eliminate the pistol grip feature,
you may not have a flash suppressor or a muzzle that is "threaded to
accept a currently manufactured flash suppressor." A compensator or
recoil reducing device is acceptable as long as it is attached permanently
by pinning, welding or high temperature silver solder or attached with a
thread pattern for which there is no flash suppressor made.
[This message has been edited by dZ (edited November 11, 1999).]