removing 100mph tape residue...

Forgive me if this is not the right forum to post this?

I have a bunch of old Colt 20 round magazines that have 100mph tape on the bottoms. I have removed as much of the tape as I could but I am still stuck with allot of residue that refuses to come off. I have tried Denatured Alcohol, Acetone, and hot water with laundry soap.

Can anybody tell me what I can use to remove this sticky residue on these magazines?