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Posted: 3/11/2009 1:12:05 PM EDT
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Hey Guys, What kind of accuracy are you getting out of your Eotech equipped carbines at 100yards?
After you tell me that perhaps you can help me solve a problem by reading and replying to the below fact situation. I purchased a RRA CAR A4 upper and put it on my DPMS lower, which made for a very cost effective and well equipped AR. Found a Guy who would swap me the carry handle for an ARMS-40L. So with all that worked out I used the money I didn't spend on a complete RRA rifle and purchased an Eotech 511 to put on top. So I took it out to the range with some XM193, the Winchester Equivelant of XM193 (whatever we call it), and some Black Hills 60gr SP. I decided I'd sight it in at 50 yards to utilize the Revised Improved Battlesight Zero. At 50 yards my carbine seemed to like the Black Hills Fodder the best. I was getting 5 inside an inch or better. Then I moved the target out to 100 yards and my groups opened to 3 inches at best while using the Black Hills stuff. The target I was using was the NRA standard 100 yard small bore rifle target with with an inch white circle in the middle of a 6 inch black circle background. Part of the problem I have is that the NRA target causes my eyes to strain to the point that the dot seems to wobble in my sight picture. This is exacerbated by the fact that I am becoming a little bit nearsighted because I am a law student who spends his whole day looking at books 18 inches from his fact. Also I noticed that my groups shrunk when the sun finally went down and I was able to turn the power on my optic down to the point where my dot was very faint. At that setting it was dimly visible, with less bloom, and therefore smaller and more precise. I'm not interested in zeroing the rifle at 100 yards, but I'd like to make sure that the group is centered above the bull somewhere to make sure that my 50 yard zero is representative of my vertical alignment at further distances. So what is a better target for getting a consistent sight picture with the Eotech? |
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http://www.eotech-inc.com/documents/M16A4-M4MWS_EOTech_Live_Fire_Target.pdf Here's the EoTech 25 meter target to zero the EoTech. I'm not sure what you're looking for, but here's a good place to start. |
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Thanks for the extra info, and the target.
I'm sorry if I wasn't clear before on exactly what I was expecting. My concern starts with this: generally with fine open sites, from a bench, even with my eye sight I can do around 1.5 MOA. That's with a rifle that has something like a pointed pyramid type front sight such as an M1917. Being able to get groups like that means that I am able to ensure that my vertical alignement at closer ranges matches that of my longer range trajectories. Consider that if my vertical alignment at 100 yards is off by an inch with any given rifle, all things being equal, excluding things such as trans-sonic turbulance, wind, temperature, bullet balance, etc. My bullet's distance from zero at 100 yards should be represented incrementally at longer distances, ie, 2 inches from vertical at 200, 3 inches at 300, 4 inches at 400. But if my zero is off vertical at 100 yards it will be obvious and I am definitely going to take measures to fix it. Therefore, for the purposes of this discussion I will assume that the maximum amount that I would be likely to misjudge my groups deviation from vertical would be 1/3 or to make things simpler .3 inches. That means that at 200 yards my distance from vertical would be .6, at 300 it would be. 9 and at 400 it would be 1.2. Those I think are deviations that I would be willing to deal with. My problem with zeroing at 25 yards is this. Any deviation from the vertical axis which would be represented at longer distances is more difficult to detect. Because of the size of the hole punched by a .223 projectile and the inherent human error that would be present in firing lets say just a 3 shot group, an actual variation from vertical (for the group as a whole) of as much as 1/4 inch could be difficult to detect. that would mean that at 100 yards I could be off by as much as an inch, which would mean 2 inches at 200 etc.. That for me is an unacceptable deviation from vertical by the group as a whole. So I can try and zero at 25 or 50 and that is fine, until I move the target out to 100. What happens then, because of the imprecision of the relation of my reticle and my aiming point is that, while I may be able to shoot a 3moa 5 shot group at 100 yards (lets say it's 3 inches from the vertical axis to the left), what seems to happen is that when I let the rifle cool and shoot another group it, almost invariably, ends up being 3 inches from the vertical to the right (a dispersion of a total of 6 inches). So then I let it cool a gain and set behind the rifle and make another group and it winds up being 3 moa right above center. So I am left wondering which group is actually representative of my rifle's actual vertical alignment at 100 yards since now I have a pattern that is fine on the horizontal but which spreads 6 inches across the vertical axis on the target. there could be any number of reasons that a deviation at 25 yards would be hard to detect, the principle is that the closer you zero, the more pronounced any deviation might be at longer practical distances, I personally have settled on 100 yards as a good "bench mark" for testing my accuracy (I don't mean precision) of my zero. This inconsistency was not a problem at 50 yards since I cold see the edges of the white 1moa center circle outlining the border of my sight's dot. But you move the target out to 100 yards and I can no longer use the white dot as a reference but have to attempt to center it as best I can in the middle of the 6 inch (or 8 inch I cant remember) black circle. In that setup my ability to gauge the border of the target outlining my red dot is much less precise. That combined with the fact that the strain to my eyes trying to center the dot in such a huge black hole causes my dot to appear to wobble, as if it is orbiting it's own center, results in me having a hard time getting a consistent pattern to check my vertical alignment at that range with that target. I imagine that a similar target, perhaps with different colors, and larger center points, might make it easier to be more consistent in my placement of the dot and might cause less strain therefore resulting in actually smaller groups. What I am trying to figure out is what targets the members of this forum might have had more success with in getting a more consistent sighting pattern at 100 yards. 3moa is fine with me, so long as I can eventually figure out a way to get that 3 moa to stay in the same place from group to group. For example I have found that sometimes diamond shaped targets are easier to get smaller groups with while using a scoped rifle with cross hair reticles. My hypothesis being that I can align the corners of the diamond with the vertical and horizontal cross hairs thereby having five reference points (center and four corners) rather than just one reference point (the center) on a standard bullseye type target. I imagine hat something circular might be better in the instance of a red dot type scope since of course the dot is circular. I'm just wondering what type of target people have had the most success using at the range of 100 yards while using Eotech equipped carbines. |
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