Ian points out an important optics aspect regarding light transmission--magnification vis-a-vis objective lens diameter. You have likely noticed that binoculars usually are listed as "7 x 35", "8 x 40/42", "10 x 50". That is not accidental; it is related to that 5mm pupillary expansion in low light environments. An optical device's light transmission ability to the human eye is maximized by that "exit pupil" (sometimes called the "light pencil") that gets delivered to the viewer. The 1-to-5 magnification-to-objective lens diameter relationship is intended to optimize light transmission to the viewing user. No free lunch, to paraphrase P & P.
Regarding that Win M-21.......post-war skeet gun, not a pre-war Tournament Skeet variant. It is all there, EXCEPT (expletives deleted) some previous owner sawed off 3" of buttstock length and installed a Pachmayr vented pad. It is WAY too short for me, and though the pad work is very well done such things are only incrementally less obnoxious to me than Poly-Chokes on a Model 12. Hard pass, IOW. 26", Skeet 1/Skeet 2 chokes, I think it was hunted with rather than shot competitively. Bank-vault-solid lockup. It is at ASK Defensive Training in Redlands, CA if someone is interested. 909/307-1400.