Install a Belt Mountain locking base pin. They are available from Brownells, among other places. It is a drop in replacement with one exception. You must remove the locking set screw, and using a drill press and a jig (you can make your own from wood and clamps) drill a shallow depression in the underside of the barrel. That will give the set screw a place to go. It is really very easy. Don't drill deep, just a tiny depression.