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Posted: 7/10/2008 12:26:20 PM EDT
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I just got my TA31F ACOG and mounted it up like I've seen in most pictures here with an ARMS #40L folded down behind it, which puts the back of the scope about even with the charging handle. When I bring the rifle to my eye, I find I have to do the "nose to charging handle" position to get proper eye relief. I know many here are comfortable in that position, but I've always had the tip of my nose about 2 fingers width back from the charging handle and thats where I'd like to stay. If I mount the acog in the rear most position possible on the flat top rail, I am comfortable with my cheek weld and eye relief position but I can't mount a BUIS. Am I so unusual? Anyone else operating like this? ALSO, if I adjust my eye to get en even circular field of view all the way around, I notice that the blurred shadow of the FSB is off center a bit to the right. If I push my head a little more to the right than I feel in my natural cheek weld position, I can get the FSB shadow centered under the reticle, but I start to lose the extreme right side of my circular field of view. Is this critical? Should I stay with my natural cheek weld/eye position as long as I do it the same all the tme, or do I need to force myself to get the FSB shadow vertically aligned under the reticle? Thanks for your input. |
Improper sight alignment as pictured below will cause the the poi to wander if you try to align your reticle with the front sight post Ignore the front sight post and focus on correct sight alignment and a full field of view w/o shadow. Maintaining the same cheekweld and moving the acog back depends on how important having a buis is to you. edited to add: reverse the terms scope and iron sights in this image as it is incorrect in this picture(or simply ignore the top portion) |
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I have seen some people mount the ACOG on the rail as far back as possible and mount a flip up BUIS right in front of it. While it is not optimal having a zeroed BUIS already mounted beats having to reach into your bag and put on a BUIS if your optic fails. -Bill |
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I think figure 3-17 is labeled wrong. Iron sights and scope labels are opposite. If your scope is centered to the barrel and your front sight is centered to the barrel the front sight should be visible in the center of the scope. If you are looking through the scope and see the front sight at the far left or right you can't have proper alignment between your eye and the scope. |
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Thanks for the input. It feels right that I should concentrate on a clear, round field of view that is even around the edges. I don't know why the shadow of the FSB is not centered at that point. I know its not a cowitness as is achievable on an EOTECH or Aimpoint. Maybe is related to the reflections that take place inside the scope. |
That has a lot to do with it I think. Being a magnified optic and what not there is a lot of glass in there, prisms and lenses. EOtech's and Aimpoints are kinda like windows and are more forgiving to see through. |
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From the FAQ's at Trijicon: The reticle pattern in the ACOG is formed by removing highly reflective metal from a prism mirror. This mirror is at about a 45-degree angle inside the gun sight. This means that the left side of the reticle is closer to the eye than the center of the reticle and the right side of the reticle is further from the eye. The result- the right side of the reticle is focused beyond infinity which can cause distortion on the right side of the reticle. The perceived distortion will be more or less depending on an individual's eyesight. The left side of the reticle is unaffected because the human eye has no difficulty focusing on a closer object. This in no way detracts from the performance of the scope. The image of the target area is not affected. Only the right hand side horizontal reticle line is blurry. This construction is required to achieve a parallax free vertical center of the scope, which allows the built in ranging on the reticle pattern. |
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