I didn't really know the advantage of a fixed power, but I had assumptions. I thought it was because the exit pupil diameter and the eye relief could be made to much larger/longer. didn't know why, that's just what I thought.
my wife has a fixed 4x on her 9mm carbine, because it's simple, has very easy relief and forgiving to the angle of eye to he axis, despite a small objective tube. I had assumed this was the norm for a low mag/fixed power scope.Being a 9mm she isn't really shooting anything smaller than clays at 50 yards and less. But it seemed to me that it didn't really matter where you looked through the scope, you could just about always see the reticle/light, wasn't too picky about being mounted juuust right to get a decent view or having to pain through getting just the right eye contact every time.
I have been discussing optics with my step-father for his first rifle. he has very poor vision due to a detached retina that occurred 5-6 yrs ago followed by numerous surgeries. He is getting first rifle as an AR15 that he is only interested in blasting in his yard which allows for 50 yard shots and possibly a few possibilities for 100 yards, though not many. I doubt he will shoot the thing more than 3-4 times before getting put away for years anyway, but I was suggesting with his poor eyesight, he either needed to go with a Leupold FX 6x 36mm, I assumed the 4" relief and the 8mm pupil would be generous enough to keep him from having to spend a minute lining up to the axis after every shot. or if he wanted something electronic he needed to look at a CQ reticle with drop comps like the 3x Burris Prism AR-332. I know the prism will not have the relief of a scope, but thought it may be tolerable with the low magnification and a 32mm objective, and although they don calculate the exit pupil on the prisms/dots, every time I play with one at the store it doesn't seem to matter where your eyes sit at since the focal plane moves with your eye.
Please tell me if my thinking on a low-power fixed power scope is incorrect and if increased exit pupil/eye relief is not part of the equation. I would hate for him to drop 3-400$ on something that's not going to work for him or just isn't necessary. If a variable power scope gives up no advantage to a fixed power than I would much rather see him into something like the Bushnell PCL 1x4.
http://bushnell.com/tactical/rifle-scopes/ar-optics/1-4x-24mm-throw-down-pcl (but now that I just looked at it, it's exit pupil is smaller than the fixed power's 6x.....so what gives? what's the reason for that?)
if I am incorrect that a fixed scope is going to have the advantage on the exit pupil, what then creates that measurement. is it a combination of the objective size and the magnification? does the relief have anything to do with it? does a longer relief, like 3" vs 4.5" make it easier to get on target or does that ONLY tell you where your eye needs to be for optimal viewing?
what would you recommend for a man with great difficulty getting focused on things? prism, low mag glass? any correlation between the two and ease of focusing? it's not that his vision is bad per se, it's that his eyes are slow to respond and slow to constrict/contract since e has some kind of incomplete circuitry between brain and optics.....you give him a couple seconds he can see just fine.
I hope this isn't sidetracking, I was thoroughly under the impression that for whatever reason that I never really delved into, that a fixed optic had easier/faster focus for the user.