NOT .22LR in .22 Mag.
Be very careful here, because the .22 Mag. (.22 WRM) is NOT the same case diameter as the .22 LR. It's larger, and thus you risk the very real possibility of splitting the LR case. All the "interchangable" .22 revolvers I've seen have a second cylinder for the Mag. round. Will the LR chamber and fire in a Mag. cylinder - yes, but it's not recommended, like the centerfire "interchangables".
My $0.02.
Doug444