I adore my 64.
I use a 3-9 40mm, with high/see thru rings. I leave the scope set at 8x (cheap scope or I'd use 9x) . For anything close, open sights. For reaching out further I use the scope. With this set I have quickly knocked down 10 shotty hulls at 25 yds (rapid) then swapped magazines and proceeded to bust 10 clays at 100yds (less rapid...)
I liked this setup when I was plinking in the pits. It's pretty clunky for actually carrying through scrubs. There's a fellow CGN'er that has an older fixed 4x on theirs (Bushnell? it mounts with dovetail to dovetail clamp, not rings...) who can hit the same hulls at 25, and same clays at 100 without even seeing their sight.