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Optics, Mounts, Rails and Sights If it aims your firearm, post about it here.

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  #1  
Old 03-17-2014, 5:24 AM
hex4x hex4x is offline
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Default Trouble sighting in at 100 yards

I am new to the Ar platform and I bought a 1x4 scope for my new Colt with Recon-h mount. The center of the optic is almost three inches above the muzzle. I bore sighted at 25 yards about 2 inches low. At the range it was only 1 inch low at 25 yards. At 100 yards I am shooting about seven to eight inches high and my scope has no travel up. What am I doing wrong.
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Old 03-17-2014, 7:21 AM
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Quote:
Originally Posted by hex4x View Post
I am new to the Ar platform and I bought a 1x4 scope for my new Colt with Recon-h mount. The center of the optic is almost three inches above the muzzle. I bore sighted at 25 yards about 2 inches low. At the range it was only 1 inch low at 25 yards. At 100 yards I am shooting about seven to eight inches high and my scope has no travel up. What am I doing wrong.
I was looking through some of my old threads, but I can't find a pic of my AR with 1-4X to compare.

3" above the bore sounds like a lot to me, what mount are you using?

Can't say for sure this is the source of your problem, but it can't help if your optic is super high. Lots of variance between bore axis and line of sight.

Can you post a picture of your setup?
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  #3  
Old 03-17-2014, 7:32 AM
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I used to have a carry handle upper with the israeli Suit Scope Mount. I was to say if was 7 inches above the bore.

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Old 03-17-2014, 9:23 AM
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Try turning the elevation knob down, not up. Your impacts are too high, so you want to move them down. At 25yds your impacts should be closer to 2" low, not 1".
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Old 03-17-2014, 10:03 AM
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Quote:
Originally Posted by hex4x View Post
I am new to the Ar platform and I bought a 1x4 scope for my new Colt with Recon-h mount. The center of the optic is almost three inches above the muzzle. I bore sighted at 25 yards about 2 inches low. At the range it was only 1 inch low at 25 yards. At 100 yards I am shooting about seven to eight inches high and my scope has no travel up. What am I doing wrong.
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Originally Posted by kcheung2 View Post
Try turning the elevation knob down, not up. Your impacts are too high, so you want to move them down. At 25yds your impacts should be closer to 2" low, not 1".
+1

If you're shooting 7 inches high, then your scope needs to be dialed down rather than up.
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Old 03-17-2014, 10:11 AM
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Learn the "one shot zero method" and stop wasting ammo by starting close and working your way out. It simply isn't worth the time, trouble or ammo to do it any other way.
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Old 03-17-2014, 10:20 AM
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Scopes aren't really designed for AR-15s in the spirit of its classical sighting mechanism. A2 iron sights are generally sighted in at 25 yards, 36 yards, etc. The projectile is moving upward at these distances, so the point of impact at 100 yards should be higher, so you account for it accordingly. However, if you use a scope, you may wish to zero further out and hold for distances closer. 100 yards is a canonical zero with glass since you'll always be dialing up for elevation. It will boil down to some preference and learning your scope.
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Old 03-17-2014, 12:48 PM
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Quote:
Originally Posted by kcheung2 View Post
Try turning the elevation knob down, not up. Your impacts are too high, so you want to move them down. At 25yds your impacts should be closer to 2" low, not 1".
Quote:
Originally Posted by teflondog View Post
+1

If you're shooting 7 inches high, then your scope needs to be dialed down rather than up.
Doh, read right over that part!
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Old 03-17-2014, 1:00 PM
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As folks mentioned, you need to turn your elevation in the DOWN direction as that indicates your POI (where the bullets hit) not your POA (where you're aiming).

A couple of other things:

1. The ADM Recon-H mount sits 1.93" above the rail so add that to the barrel to receiver height and you have a total of 3.15" height over bore. I only mention this so you can plug that into a ballistics calculator.

2. You're going to be shooting way high at 100y, if you previously zeroed at 25y. That's why a 25Y zero IMO is terrible. The only reason the Army does this with A2 sights is so they can use the rear elevation drum.

And it bears re-posting since someone mentioned the bullet rising:

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Old 03-17-2014, 1:19 PM
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Default Zero at 50 yds

It is generally considered that an AR15 50 yrd zero will also zero you at 200 yrds, with many variables that may change that a tad or two.
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Old 03-17-2014, 1:35 PM
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Quote:
Originally Posted by kcheung2 View Post
Try turning the elevation knob down, not up. Your impacts are too high, so you want to move them down. At 25yds your impacts should be closer to 2" low, not 1".
Yea, this, there is nothing more to say.
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Old 03-17-2014, 1:36 PM
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This is good, but the basic question is where do you want zero. With a scope the manufacturers generally suggest 100 yards (meters are close) or 50 yards (meters).

The other thing is at 1.93" from rail to centerline the mount you have is pretty high. Most of the mounts I have used are in the 1.5-1.65 range.

If I were you I'd zero at 100 yards. Using a target that is made to use at 25 or 50 yards, but gives you a 100 yard zero.

Here try these 8.5x11' targets:
http://www.m4carbine.net/showthread....mp-300M-Zeroes


Quote:
Originally Posted by SuperSet View Post
As folks mentioned, you need to turn your elevation in the DOWN direction as that indicates your POI (where the bullets hit) not your POA (where you're aiming).

A couple of other things:

1. The ADM Recon-H mount sits 1.93" above the rail so add that to the barrel to receiver height and you have a total of 3.15" height over bore. I only mention this so you can plug that into a ballistics calculator.

2. You're going to be shooting way high at 100y, if you previously zeroed at 25y. That's why a 25Y zero IMO is terrible. The only reason the Army does this with A2 sights is so they can use the rear elevation drum.

And it bears re-posting since someone mentioned the bullet rising:

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  #13  
Old 03-17-2014, 1:39 PM
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Quote:
Originally Posted by SuperSet View Post
As folks mentioned, you need to turn your elevation in the DOWN direction as that indicates your POI (where the bullets hit) not your POA (where you're aiming).

A couple of other things:

1. The ADM Recon-H mount sits 1.93" above the rail so add that to the barrel to receiver height and you have a total of 3.15" height over bore. I only mention this so you can plug that into a ballistics calculator.

2. You're going to be shooting way high at 100y, if you previously zeroed at 25y. That's why a 25Y zero IMO is terrible. The only reason the Army does this with A2 sights is so they can use the rear elevation drum.

And it bears re-posting since someone mentioned the bullet rising:


I was going to post that graphic.

Assuming one is zeroed as such that there are two points of zero as the above graphic.
It's helpful for me to picture the bullet's path as viewed looking through the scope. That it will "rise" from the bottom of the scopes field of view, reach the first point of zero, "rise" slightly above that, fall back into the second point of zero, and continue to fall.

As long as one realizes that it it is "rising" only relative to the optics perspective.

This keeps my mind straight on when to hold over and under and quickly make that decision.
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  #14  
Old 03-17-2014, 6:32 PM
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If you're trying to achieve POA=POI at 100 yards then you should be about 1.5" low at 25.
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Old 03-18-2014, 8:47 AM
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Lower your scope 6"@ 100yr & go shooting.
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Old 03-18-2014, 9:55 AM
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#1 Scope being 3" above bore is normal on an AR.
#2 With a 25 yard zero, you will hit 6" to 7" high, that is normal.

#3 You need to set the elevation knob so you shoot 6" to 7" low, which is probably the opposite of the direction you've been turning.
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Old 03-31-2014, 1:18 PM
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One shot method:

Put the gun in a vice
Aim at bullseye
Shoot
Move the crosshairs from the bullseye to the bullet hole while the gun is held firmly in the vice or even with sandbags.
Done.

This works for open sights, peep sights, scopes without markings or any other sighting arrangement.

Of course, shooting a group of 5 or so would be a more reliable way of doing it, but if you are willing to risk it, that's all you need to do. Now your crosshairs will point to where the bullet will impact at that particular distance.
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