Scopes With No Front Bell

[Critch]

I was looking thru a Weaver V3 (1x3) the other day. I want it for my Ruger M77 RSI becuase it doesn't hit the rear sight. Anyway, it seems that I can see as well as I do with my 3x9x40's. I realize that it's low power and that makes a big difference, but what does the big bell on the front of other scopes really do?

[Lone Star]

Very basically, it collects more light. The higher the scope power, the less light it transmitts. That's why a 3X scope can get by without a large objective lense, but a 9X needs a large one. The proliferation of 50+mm scopes is an outgrowth of this optical fact, allowing even more light on higher power scopes than with smaller objectives.

[Jack]

Lone Star is correct.
A very thumbnail generalization is that you'll get optimal light gathering if the front (objective) lens on a scope is 5x the power (magnification). The 20MM objective lens on the Weaver V3 gathers all the light the scope can utilize- a larger objective would add weight and bulk and give no advantage.
BTW, the Weaver V3 is a sweet little brush gun scope, and would look very nice on a Ruger RSI. Several fellows I hunt deer with (and myself) have been using the Weaver V3 for years- they hold up very well, and get the job done.

[Critch]

Thanks folks. I just ordered the Weaver for my rifle, they sold the one I was looking at.

I must have been asleep during the physics class that dealt with optics, I have never understood lenses and such.