Same thing on my Savage, I drilled and tapped the ring mounts to fit the widest screw that would fit, and selected a bolt of a length that fit perfectly the width of the ring mount. Then I tightened it down really tight. It helped, but after about 500 or 600 rounds at the Appleseed it finally began creeping forward again. I tried drawing a tool down the dovetail and stopping just before the end of the dovetail to create a bit of a ridge for the clamp to catch on, and tightened the mounts really tight, but haven't shot it since then. I'm thinking that if it persists, I'll either drill and tap the receiver and put in a screw to stop the mounts from creeping forward, or I'll get those Weaver mounts that fasten to a dovetail, and put a set screw in them with a detente drilled into the receiver for the set screw to hold in.