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Old June 28, 2012, 08:44 AM   #1
MTG
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Red dot sight...where to sight?

I have a red dot sight on my AR that I zeroed at 25 yards. At first, I was surprised how low I was hitting the target at 10 yards. It was easy to see why it was so low because the red dot sight is mounted on top of a scope (I'd estimate about 6 inches above the barrel).

My question, what's the best option for consistency with this setup? Seems like the best way would be to set the sight to have the round hit 6 inches low (assuming it's actually 6 inches above the barrel). Does that sound logical? I'm not trying to win a competition with it or anything...mainly just use the red dot sight for fun at the range. Only other scenario I could ever see myself using it is if I'm attacked by a horde of zombies
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Old June 28, 2012, 10:19 AM   #2
Art Eatman
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Six inches above the barrel? Zeroed at 25? You'll be higher'n a cat's back at 100.

With a scope 2" above the barrel and zeroed at 25, I know that I'm commonly a couple of inches high at 100. I dunno. I'd start with 4" low at 25 with your rig, and figure that it would be on the paper at 100. Then go from there.
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Old June 28, 2012, 10:29 AM   #3
insomni
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mmm..... no. the drop offset is affected by the height above the barrel, but not in that 1:1 sort of way. (6" is REALLY high for any sort of optic... pics?)

How low ARE you hitting? My experience has been that rounds tend to fall about 2 inches low in close when zeroed to 25m. Solution for that is to adjust your point of aim in close (2-3" higher)

if you want to zero it to 10m, you're going to have to compensate when firing at further distances (yes I know the 25m zero actually has to be tweaked at distance anyway)

Last edited by insomni; June 28, 2012 at 10:45 AM.
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Old June 28, 2012, 03:13 PM   #4
eldorendo
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I have a red dot that's mounted on the side of the scope, and that arrangement works pretty well. I wouldn't want any kind of optical device to be 6" above the bore.
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Old June 28, 2012, 06:32 PM   #5
jmr40
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With mil spec A-2 rifles with standard irons a 25 yard zero is also a 300 yard zero. With the red dot that high it would probably be useless beyond 50 yards unless you are aiming at someones feet.

Use either the red dot or the scope, don't try both at the same time unless you try some of the mounts that place the dot sight at a 45 degree angle to the side of the scope.

http://www.mountsplus.com/AR-15_Acce...WVR-99671.html
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Old June 28, 2012, 10:04 PM   #6
arizona98tj
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Pull the red dot off of the top of the scope and stick it in the parts drawer for use on some other firearm requiring a red dot. Learn how to properly use the scope.

Or....do the opposite....pull the scope and put the red dot on the rail.

Either way, you'll become a better and more consistent shooter, IMO.
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Old June 29, 2012, 06:20 AM   #7
MTG
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I have it set now to hit about 4.5 inches low @ 10 yards. It's actually 4.592 inches from middle of barell to middle of red dot.
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Old June 29, 2012, 08:15 AM   #8
Art Eatman
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At some point you need to see where that hits at 100 yards, and on out to 200 or more if you have access to the longer distances for your shooting. Again, guessing, an inch--maybe two inches--low at 100 would be close to dead on out around 200.

I dunno. I wouldn't set up such a rig. My AR is set up for plinking and varminting. It's a flat top with no front sight, and a Weaver K4 on top. Just under one MOA with most any 50- or 55-grain bullet.
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