Scope mounting problem?

I'm having difficulties mounting a scope onto my Savage Mk. 2 G .22 rifle. It is a pre accu-trigger and is not drilled and tapped for mounts. I believe it has a dovetail (groove running down the middle of the receiver on top, I'm not too experienced with scope mounting terms) to mount the rings to.

Anyway, I tried mounting a set of Weaver brand 1" medium rings to it (using a 3-9x40mm scope w/ 1" tube). The rings are supposed to fit a 3/8" grooved receiver. After I snugged the rings down (pretty tightly) and fired a few shots the rings had basically slid all the way back and off of the dovetail. Is there a special trick to secure these things down or did I just get the wrong rings? It seems like there is nothing to hold the rings securely in position to prevent such slippage.

I've mounted a few scopes before and never ran into this problem. I would prefer not having to take this to a gunsmith.

Please help! Thank you!!

Can you post pictures of the receiver and rings?

If they slipped back twords the butt then it sounds like they were not tightened securely. The recoil of the .22 long rifle cartridge is minimal and I've never heard of it moving a scope especially one that was properly tightened. Usually recoil slides the optic forward tword the muzzle not the butt. Did you set the rifle down hard on the butt a couple of times? That would move the scope in that direction if it weren't tight.