Scope Objective Size vs Magnification

[Phil3]

I am building a 6mmBR rifle to shoot mostly at 100 yards, some at 200, rarely at 300 (nothing else around here), and while I want a quality optic, don't want to spend money on things I don't need. I can cut cost by buying a scope with an objective only as large as needed. My question is there some point in magnification where the objective size becomes inadequate due to light gathering ability? The worst situation I will be shooting in is overcast, but most of the time it will be sunny. I don't want to buy a 50mm objective if 44mm will do the job. I tend to shoot at high magnifications, but I am not convinced that is helping my shooting. 20x at 100 yards does seem excessive. ??? I am also thinking that a fixed focus scope would allow higher light transmission, perhaps making the smaller objective perform a bit better than a zoom scope. ??? The fixed focus would also cost less.

Phil

 

[JohnHenry]

Phil3, You may find the following article on exit pupil of interest.
http://www.shootingtimes.com/2011/01/03/optics_opticpupil_061907/

Also check-out this site's article on target scopes.
http://www.accurateshooter.com/optics/target-scopes/

 

[Raythemanroe]

http://www.bigsupplyshop.com/Sightron-SII-36x42mmBRD-Dot-AO-30156_p_3822.html

 

[Phil3]

With regards to exit pupil being calculated by dividing objective size by magnification, and 2.0 mm being often considered the minimum, it surprises me people seem very satisfied with the Weaver T-36. That has a exit pupil closer to 1 than 2.

I am not sure if 36x is too much for 100 yard shooting. Wish I could try one out at that distance.

Phil

 

[JohnHenry]

Phil3, I have both a Weaver T24 and a T36. The T24 is also a nice scope for the money and I find fine for target shooting at 100 and 200 yards. Exit pupil of the T24 is obviously larger(1.67mm). Can still see 22 cal bullet holes at 200 yds with the T24 and mirage is less of an issue than with a 36 power scope.

 

[MK 19]

I know that we are only talking about 100-200 yards, but your optics are still the last item that you need to be reducing the quality of, after all the scope is the most important part of any build, you can't hit what you can't see

 

[Phil3]

John,

I am liking the Weaver 24x, since I know 24x works OK for me at 100 and I have shot it out as far as 300 and it was still OK. Admittedly, 24x at 100 seemed almost too much. It seems then that a 24x would be ideal, but John, did you find brightness OK with the smaller objective. I have only shot 24x with a 50mm objective.

MK 19,

I know about not cheaping out on optics. My last rifle build is wearing a Vortex Viper PST 6 - 24 x 50 scope, not a cheap piece, at least by my standards. No Schmidt & Bender, but pretty good I think. What I am trying to do is spend money on the optic where it makes sense. If I hardly use the zoom feature, then why pay for it? Makes better sense I think to invest in optic performance vs features I may not use. I appreciate your input.

Phil

 

[JohnHenry]

Phil3, I find the brightness of the T24 just fine for my informal benchrest shooting. Have used it out to 400 meters on a 223AI and in ideal conditions the resolution is adequate to see 22 cal bullet holes on a light colored background. The T24 and T36 are both still made in Japan, a plus re. optical quality in my view.