Leupold also makes a 1-4X20 shotgun/ML scope. Nikon also makes a shotgun scope that is excellent.
I have several of the Leupold scopes that you are referring to. Three of the 2-7X33 and two of the 1-4X20. But none of these are on a shotgun. I use them for my close range carbine style rifles and a 50Beowulf. I have two of them on my Handi-Rifles chambered in 45-70 and 444Marlin. One also on a 20" 45-70 bbl for my Encore Pro Hunter.
To your question......I do not know why the limited choice of objectives. But.......just guessing
* these scopes are designed to be used at the closer ranges where light transmission is not as critical
* they want to combine a good field of view and a longer eye relief into a scope that is used for the harder recoiling firearms.
As long as the objective diameter stays reasonably close to the power range you do not loose very much,if any,light transmission.
The formula used is this ---> the human eye can dilate to 5mm for you young folks and about 7mm for us older guys. So take the 7mm and divide it into the objective diameter. That is the highest power that the variable scope should be set at to use all available light. For you younger guys use the 5mm figure and the 33mm scope. 33 divided by 5 is 6.6. The scope's max is 7x. You can use this formula with any scope. Keep in mind that the quality of glass along with it's coating,makes a huge different in the light transmission to your eye.
While coyote hunting in Maine in the early morning or late afternoon,I would use my 24" AR with a 6.5-20X50mm Leupold. No matter how far out the yote was. I never cranked the scope up past 7X or 8X. This,for a clearer view of the animal.
All you deer hunters should keep this in mind also. Especially all of us that have to see/count horns/points. ---pruhdlr
