AR-15 scope trouble

[Gater]

A friend purchased a Greatlakes AR-15 I sold him a
Nikon 4-12 BDC i had that scope on my AR shot great all I did was slide it off my rail and on to his tried to sight it in and ran out of elevation on the scope. Any ideas why it would be that far off it is about 2’ low.at 100

 

[acloco]

Front of the receiver is not square with the world on the new rifle.

 

[Gater]

Any ideas on how to correct this ? Or better to contact maker ? Thanks for the help

 

[Brians356]

all I did was slide it off my rail and on to his tried to sight it in and ran out of elevation on the scope. Any ideas why it would be that far off it is about 2’ low.at 100

Are you saying it's 2 feet low even at the limit of elevation adjustment?
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[Gater]

Yes it was still shooting in the dirt at 100 yds and there’s no more elevation. I had trouble with a different AR years ago but it was windage and iron sights

 

[Brians356]

Yes it was still shooting in the dirt at 100 yds and there’s no more elevation. I had trouble with a different AR years ago but it was windage and iron sights

It could have one of several causes, but I'd put the scope back on your AR and verify it still works fine on your rifle. That would cross off the list that something shifted or broke internally, as unlikely as that seems. You've got to start the divide and conquer somewhere, and even the finest scope is more delicate than a rifle.
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[Lone Hunter]

Is his a canted rail? If not you might want to get Burris Signature Rings with the inserts. I have not had trouble on an AR but on a bolt gun I had a 20 moa rail on it and I could get it no closer than 6” low at 100 yds. I went back to a 0 moa rail and zeroed at 100 and still could go to 1000 with the inserts. My scope only had 42 moa up and 44 moa windage. NF 12-42 BR. Check out the Burris Signatures if you cannot get it zeroed.

 

[justpassinthru]

Front of the receiver is not square with the world on the new rifle.

This absolutely can be the problem. I bought an AR15 once at a gunshow on which the rear sight had to be moved to the end of its travel to zero the rifle. After I removed the barrel and trued the receiver, the rear sight was in the center when zeroed and all was well.
It's my understanding the receivers are most likely true but the coating can vary in thickness causing the problem. On the rifle mentioned, I could clearly see the receiver was high on one side and I removed the finish until I saw white aluminum all the way around.

 

[Gater]

Thanks guys I think we will put it back on mine and start ruling things out

 

[Brians356]

Thanks guys I think we will put it back on mine and start ruling things out

Meanwhile if it has iron sights (I suspect not) see if they allow POI on target. If not it suggests receiver out of square.
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[jisco43]

Is his a canted rail? If not you might want to get Burris Signature Rings with the inserts. I have not had trouble on an AR but on a bolt gun I had a 20 moa rail on it and I could get it no closer than 6” low at 100 yds. I went back to a 0 moa rail and zeroed at 100 and still could go to 1000 with the inserts. My scope only had 42 moa up and 44 moa windage. NF 12-42 BR. Check out the Burris Signatures if you cannot get it zeroed.

Agree with the Burris Signature Rings. I've used them and love em!