I have a Beeman RS2 pellet rifle and want to mount a scope or red/greed dot sight. but all I see are ones for 11mm or 20mm and when I measure the Beeman it is .466 in or 11.84 mm What is the correct scope mount for this pellet gun. It seem like it has a strange dimension. my 22 rifle is .433 in. or 11mm. Thanks for your suggestions