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Posted: 7/29/2009 9:45:48 PM EDT
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Greetings. Lately, my range outings are giving me curious results. While having a blast shooting tons of ammo, I thought that I finally figured things out. However, the holes in the paper don’t equate to my understanding of the optic. Considering my eyesight, my Troy BUIS work as advertised – no problems.
Equipment TA11 ACOG donut reticle LaRue Tactical LT100 QD Mount Colt 6920 PRVI SS109 Q3131 I store the gun with the optic mounted, and remove it while cleaning the gun, or using iron sights. Some of the old-timers at the range laugh when I remove the mount, and I told them that it was designed to do this. (They have never seen the QD mount) [edit 1 - question answered] 1. Will constant on / off of the mount affect the zero? I am under the assumption that the mounts are stable enough to allow this with negligible impact. 2. Is my understanding of the ACOG ranging correct? Top of reticle = 100 meters
Center = 50 / 200 Bottom = 300 Weeks 1 and 2 shooting prone with sandbags using PRVI SS109, 10 round mags. Each outing shot average 100 rounds, splitting between BUIS and ACOG Week 1 - zeroed at 100 meters using the top of the donut centered on the target, 30 rounds, averaging 2.5 to 3” center mass with a couple of fliers. Week 2 – 50m using the center of the donut. Group of 20 about 1.5 – 2”, center of group offset Y + 1, X + 1. Week 3 – shooting on a solid bench, sandbags, 100 meters, using both Q3131 and SS109, top of the donut. I also put black electrical tape over the fiber to prevent blooming of the reticle. Both ammo types shoot identically. Both 20 round groups are about 3”, but are centered about 2” high. I then moved the target out to 200 meters, using the center of the donut. The 20 round group was centered about 5 inches high. It took 12 clicks down to get the rounds to hit center mass. 3. By eliminating the external light from entering the fiber, thereby preventing blooming of the reticle, does this affect the point of aim? 4. Is there a difference in sight picture between prone and a bench rest? [neck position?] The problem is probably between the scope and the trigger. Appreciate any guidance, insight, flaming,… |
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I can't answer all of your questions, but regarding the removing/replacing of the LaRue mount...
check this thread out |
There should not be any difference between a lit and unlit reticle. The BAC equipped ACOGs reticle can be very bright and somewhat distracting when taking careful aim, so the cover/no cover thing is a preference, I did notice that on my TA31DOC (fine cross hair) when it's brightly lit, the cross hair seems to be slightly thicker from the glow. Once covered, it's the thin black lines again. I wasn't any more accurate with the fiber optic covered though 
There should not be a difference between shooting positions. |
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Our zeros were a 45-250m zero, with IMI m855, as follows:
25m: -4 cm 45m: 0 100m: +7 cm 200m: +11cm 250m: 0 300m: -20 cm 400m+: BDC FWIW this seemed to work for Minute-of-Syrian-soldier-head-target. 
When we were shooting at heads, I used the following guideline and it worked fine: 0 - 50m: center of head 100-200m: chin 250m: center of head 300m: POI between bottom of donut and the first hash mark in the BDC |
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From what I have gleaned from your data, the 50 (center of donut) = 250m.
I have read elsewhere that: 100 = 0 MOA 250 = 2.06 300 = 3.5 If the outside diameter of the donut is 4 MOA, and the inside = 2, then your data makes sense. Therefore at 300m, the POA should be at 7/8 of the donut instead of the bottom?? Link Thanx again for the help edit: not sure if different shooting positions may also affect the outcome? |
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After further research, I have read that others have experienced a different POI between shooting positions. Most are complaining that a bench zero will shoot low during prone, say 4MOA.
If this is true, then I feel better about my equipment and is just a matter of training differently. I will go back to my original zero, for the only way that I can take the bench w/ me during a SHTF situation is to put wheels on it :) Thanx all for input ///////////////////////////////////////////////// UPDATE: After further analysis, I realize that my problem was the result of a bad sight picture, and not necessarily my shooting position. I moved the ACOG further forward to optimize the longer eye relief, getting my nose on the charging handle, thereby giving me repeatable shots. I also confirmed that inconsistencies in eye placement causes parallax which messes with my brain...... The "I-D- ten-T" error message keeps popping up Conclusion: Like golf, concentrate on correct techniques and you to can get on the green w/ less shots and avoid the sand traps! |
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