I have a .22 mag (off the rack of a general store, obscure name) that is not drilled for a scope mount. Instead it has two grooves, one either side of the receiver crown running longitudinally on the receiver. Does anybody know what kind of scope mount it would use? I'm thinking of putting on either an old full size Tasco scope that I don't trust for full size rifle loads (the poi keeps moving) or an old 4X .22 Weaver scope, and I suspect one mount won't fit both.

paa,
You need dovetail rings, common to the .22`s and including the .17 rimfires. Most are commonly available at your retailer or smaller gunshops. Some of the 1-inch tube diameter scopes provide very little room forward of the receiver port for ring placement. I usually mount the front ring right on the edge of the receiver in order to detect any movement after several boxes of ammo. It will tend to move forward, due to continued recoil. Matching it on the edge allows you to easily see or feel if it has moved forward.
The older rimfire scopes tend to be longer in front of the adj. turrets. Current "bargain" rimfire scopes offer very little fore and aft adjustment, so eye relief may be a bit too far forward...

Thank you.