A scope needs an Adjustable Objective--an 1/8 or 1/4 dot reticle -20x to 24x is good for the rams. The down side it takes a while to become accustom the the "wiggle" of the cross hairs at full power of 20x to 24x. -Turrets are a must as well.
These three are affordable:
Sightron SII Rifle Scope 6-24x 42mm Adjustable Objective 1/4 MOA Dot Reticle Matte
Product #: 752043Manufacturer #: SII624X42D-HAS TURRETS/1/8 MOA CLICK
Bushnell Elite 4200 Rifle Scope 6-24x 40mm Adjustable Objective 1/4 MOA Dot Reticle Matte
Product #: 322574Manufacturer #: 426243A---HAS TURRETS/1/8 MOA CLICK
Weaver Classic V-Series Rifle Scope 4-16x 42mm Adjustable Objective 1/4 MOA Dot Reticle Matte
Product #: 237655Manufacturer #: 849410---HAS TURRETS/1/4 MOA CLICK