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Posted: 3/3/2009 6:24:25 PM EDT
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Because I don't have the greatest eyesight, I'm now thinking I may go with ACOG, but still may go with the Aimpoint T1 + 3X magnifier on a pivot mount. I've been researching ACOGs and reading all I can, but I noticed that the popular TA11 series seems to be about 2-3 inches longer and a couple of ounces heavier than the TA31 series that has more magnification. Understanding that there are a million variables with these, I'm trying to determine why the big size difference. For my rifle, I'm looking at: TA31F-G: 4x32 Trijicon ACOG: http://www.trijicon.com/user/parts/products1.cfm?PartID=716 TA11F-A: 3.5x35 Trijicon ACOG: http://www.trijicon.com/user/parts/products1.cfm?PartID=415&back_row=3&categoryID=3 I'm still thinking the Aimpoint combo may be more versatile for me, but I'm not sure, so feel free to comment on that as well. I'm not LEO or Military, but this will be used as range and tactical course rifle as well as a personal defense weapon. Thanks in advance. |
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Quoted: Eye relief and exit pupil. Thats why. Can you elaborate a bit? I'm not really up to speed on the in's and out's of scopes. What/How does eye relief matter to your setup? Exit pupil? Does field of vision vary greatly between similar power scopes or do higher end ones have larger fov's? Some scopes/ACOGs have smaller tubes which seem to make it more difficult to use... is there an advantage to a smaller tube (my common sense tells me a bigger tube is easier to use)? |
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Quoted:
Quoted:
Eye relief and exit pupil. Thats why. Can you elaborate a bit? I'm not really up to speed on the in's and out's of scopes. What/How does eye relief matter to your setup? Exit pupil? Does field of vision vary greatly between similar power scopes or do higher end ones have larger fov's? Some scopes/ACOGs have smaller tubes which seem to make it more difficult to use... is there an advantage to a smaller tube (my common sense tells me a bigger tube is easier to use)? I will try to explain as best I can. Well... longer eye relief, all things being equal, reduces FOV. Its an inescapable fact. The TA31 has a super short eye relief and a super wide FOV. You are crammed right up to the occular and you will get the scope to tap your shooting glasses once in a while. This is extremely annoying/uncomfortable for some people and in larger calibers this means you will get an eye full of scope. On a 5.56 this is mostly perference and due to M16 iron sight users being trained to shoot the ghost ring sights with a nose to charging handle hold the TA31 requires that kinf of head position. Exit pupil, for lack of a better descrioption, is the size of the "beam" of light coming out the back of the scope. This has 2 effects. For high powered scopes you must keep exit pupil above your eyeball's pupil size or you will have reduced brightnes in low light. Here this is a non issue as the 8mm exit pupil of the TA31 will yeild maximal brightness in all lighting conditions since your pupil cant get to even 8mm. However the 10mm exit pupil of the TA11 means you will have more leeway in head position without getting black cresecents blocking some FOV. Exit pupil is Objective size divided by magnification. The TA11 is 35mm and 3.5X so 10mm, the TA31 32mm and 4X so it is 8mm. Larger objectives result in larger and havier scopes. Field of view varries greatly between scopes, even in the same magnification range, and has nothing to do with "quality" it is just a mathmatical issue that has many variables, the most important of which is an inverse relationship to eye relief, or the distance you should sit back off the scope to get a propper view through the scope. I is a trade off with eye relief or the distance you sit back from the scope, all things being equal, but other things can effect it as well, primarily magnification, but alos the size of the scopes objective and overall size come into play. To see the trade off bewteen objectve size/magnification/FOV... look at the 3X compact ACOG. The original TA50 had the same short eye relief of the TA31. The long eye reilef 3X ACOG TA33 is a longer scope and has a very narrow FOV but a larger exit pupil since it has a larger objective and the same magnification. This makes it more comfortable for some people to use but it makes the scope larger and heavier.  
TA33 30x3 = 10mm exit pupil, and 1.9" eye relief TA50 24x3 = 8mm exit pupil and 1.4" eye relief  
TA11 35x3.5 = 10mm exit pupil and 2.4" eye relief TA31 32x4 = 8mm exit pupil and 1.5" eye relief Note when you want to increase both eye relief and exit pupil on the full size or compact ACOG to make the scope more "user friendly" you increase scope size and decrease FOV. This is a trade off. Is it possible to have a longer eye relief AND a wider FOV? Sure but it would require a MUCH larger scope, or MUCH less magnification, so to maintain similar sizes and weight these things become a trade off. When it comes to variable scopes you will note if they are the same genreal size and objective diameter, say both 3-9x40, and both the same general length, the one with the shorter eye relief will have a wider FOV at all equivalent magnifications... but of course the scope with the "narrow" FOV will have a wider FOV at much lower magnifications. |
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