What discipline are you shooting? If bench rest, I would just get an optic that could do both. My 4.5-27x50 HD scope that can spot 22s at 50 no problem
Fair enough, I don't have any suggestions for one of your criteria being a 50mm. Personally, I would opt for a larger objective if light gathering at that distance is an issue. I have a Bushnell 15-45x60 and used it at 50 yards out to 200 yards to spot 22 on paper.
Nikon ed50 has had many many glowing reviews for many years...you can pick them up fairly cheap from nikon dealers in Japan on eBay. I think one of them might be on amazon as well
Aprochromatic Lens System: Apochromatic lense system gives you the result of images which have greater contrast, sharpness and color definition
ED Glass: ED glass gives you an image with little or no chromatic fringe so the final result brings a clearer and sharper image to your eyes
ESP Dielectric Coating: ESP Dielectric Coating is a multi layer prism coating that reflects over 99% of the light to your eyes bringing you a clear, bright image that displays accurate color reproduction.
Magnesium Chassis: Magnesium chassis give you the strength of a metal chassis while reducing the weight as much as 30%
XPL Coating: XPL Coating gives you an extra protection on the exterior lenses from dirt, oil and scratches
Bak4 Prism: Bak-4 glass prisms reflect more light to your eyes which will give you brighter and sharper image.
Advanced Fully Multi-Coated: Advanced Fully Multi-Coated lenses gives you better light transmission to bring optimum brightness and true color across the entire light spectrum.
Argon Purged: Argon Purging uses the inertia gas with bigger size molecules to purge any moisture out of the tube giving you better waterproofing and thermal stability .
Waterproof: Waterproof to protects the binocular in the harshest weather conditions or if accidently submerged underwater
Dual Focus: Dual focus has dual speed focus knobs that offer both faster and finer focus adjustment
Rotating Ring: Rotating Ring allows you to rotate the scope around tripod supporting ring into the most comfortable and convenient angle for observation