As Charlie said the M1E7 was an experimental scoped carbine using a Weaver 330 commercial scope. In a nut shell the mount was very stable but the scope took a beating. By a little less then 3000 rounds the scope was destroyed internally from the forces of the brass hitting the scope. The mount went on to be used in the T3 night vision system. But the scoped M1E7 carbine was never adopted in any form.