Scope on an AR-15 with carry handle

[Street Rat]

I have an AR-15 that I have mounted a scope on top of the carry handle. I figured with the scope being mounted so high there would be challenges. The last time we went to the range I tried to site it in at 25 yards, we got pretty good then I went to 50 yards and from there it went all down hill. We went corner to corner and had a real hard time finding a bullet even hitting the target. Would it have been best to try to sight this in at the 100 yard range with this kind of set up? Is there going to be this big of a difference between 25 to 50 yards?

 

[MinnMooney]

I'd have to know what the distance is from the barrel center-of-bore to the scope's center. Most ballistic tables assume (incorrectly, most of the time) that the distance is 1.5" but that is rarely the case with an AR-15.
If your bore-to-scope distance is about 4" & you "zero" at 25 yards, you are also "zero'd" at somewhere around 500-625 yards (depending on your ammo).
My neighbor has high-rise, sight-thru scope mounts on TOP of his carry handle so his bore-to-scope is over 5". He zero'd at 25 yds and found that at 100 yds he was shooting 22" high and his second zero was at 750yards!!
Zero'ing your rifle at 20-25 yards only works if the bore-to-scope distance is approxapately 1.5"

 

[MinnMooney]

If you're going to use you blk gun in a hunting scenaio where they say you can hold dead-on at any range up to some given distance and be +/- 3" then that given distance would be 305 yds. if your bore-to-scope distance was 4" (not including the first 15-18 yards where you'd be 3"-4" low).
If your B-to-S distance was 4.5" then your dead-on hold would be out to about 325 yards.
I hope that I'm explaining this correctly and clearly but I realize that without a ballistics graph to look at it's difficult to visualize.

 

[benEzra]

Measure vertically how far the scope sits above the line of the bore. Then zero the point of impact just shy of that much low at 25 yards, to get you started (i.e., if the sight sits 3.5" above the bore, sight it so that the bullets impact 2.5 to 3 inches below the bullseye at 25 yards. Hopefully this will get you on paper at 50.

Once you're at 50, you can zero right to point of aim and you should be on paper at 100. Move back to 100 and adjust your zero, and you should be pretty close.

 

[Street Rat]

Thanks, this is all good information. I'm going back to the range next week and I will use all of this information.

Stay tuned for questions about a scope that I have put on an SKS.

 

[Lonestar.45]

Stay tuned for questions about a scope that I have put on an SKS.

Don't do it. Not if you're going to use a receiver cover mount. They move around and are worthless IMHO, been there done that. I would not scope an SKS, but if you're going to, you need to do it right and find a mount that is tapped and screwed directly into the side of the reciever. Hard to find and still doesn't make the SKS a tack driver, but that's the best option.

 

[romma]

convert to flat top... Mine cost $134 to make the conversion. Including labor and headspacing. (Another option)

 

[benEzra]

Don't do it. Not if you're going to use a receiver cover mount. They move around and are worthless IMHO, been there done that. I would not scope an SKS, but if you're going to, you need to do it right and find a mount that is tapped and screwed directly into the side of the reciever. Hard to find and still doesn't make the SKS a tack driver, but that's the best option.

The Millett scope rail that replaces the rear sight blade is reportedly solid and requires no permanent alteration to the rifle. Here's one with a red dot on a Millet mount, courtesy of Calguns:



http://www.calguns.net/calgunforum/showthread.php?t=22699
http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=595160

 

[Street Rat]

Don't do it. Not if you're going to use a receiver cover mount.

Thanks, that is what I was going to ask and I already have done. We tried to sight it in and was not at all cooperative. I still have my original cover I will put back on. I thought that it was just maybe me when I was filing the new top cover. I'm not much of the gun smith. I was'nt really sure about the pictany rail with the scope sitting so far forward.

 

[W.E.G.]

A scope mounted atop the charging handle is probably about three inches above the bore.

In that case, this trajectory chart would apply.

 

[W.E.G.]

By contrast, the same gun, if zeroed for dead-on at 25 yards would deliver bullets 7.5 inches high (above point of aim) at 100 yards.



The point of impact at 100 yards would be even higher if the scope is more than three inches above the bore. Similarly, the point of impact would not be quite as high if the scope is lower than three inches above the bore.

The closer to the bore the scope is mounted, the more the "point-blank" range improves.

 

[benEzra]

I was'nt really sure about the pictany rail with the scope sitting so far forward.

That style (the "scout scope" concept) requires either a pistol scope or an unmagnified red dot style sight, i.e. something with very long eye relief. A traditionally styled rifle scope won't work that far forward.