sight in issues... help

[tjones96761]

First time AR owner. I have a Stag M6 (flat top upper, bull barrel). Mounted a Burris Fullfield 3-9x40 with Weaver rings to the integrated rail and went out to sight in.
first off, it isn't even on an 6'x6' backboard at 100 yards. step up 50 and it's 2' high and 2' right. dial it down and in and back up to 100 again. Still high, adjust the scope all the way down. and I'm still 6 1/2" high. check everything for tight and it's all good. completely dismantle scope from rings and rings from gun and remounted this time with the front and rear rings swapped. fewer shots but the same result. still 6.5" high.
So question is... is there something I don't know about flat top uppers? do I need a particular set of rings for an AR? Is it because I tried to use a hunting scope on a benchrest varmint rifle?
I swapped the rings for a different set but ran out of daylight before I got to shoot it. I plan on putting a 4-16 scope on the rifle permanent, I just wanted to shoot it. It shoots great by the way, 1" groups off the hood of the truck with no rest and federal bulk 55gr FMJ. If I could just figure out the too high part...

 

[ez bake]

I was going to say that I think its Weaver that makes adjustable rings - you might check on those (but now that I think about it, I think its only Windage adjustable rings). There's nothing special about putting a scope on a flat-top upper - just mount and shoot like it was on any other Picatinny or weaver-style rail.

If you ran out of adjustment, you might have a scope issue - I'd blame the rings, but if you swapped them and still have issues, then its either the gun (and I don't know that it would even fire correctly if the barrel wasn't installed even 1-2 degrees out of whack into the upper) or the scope.

Try the scope on another gun to rule it out and try another set of rings to rule those out.

Sucks that this is your first AR/ownership experience, but I'm guessing its the scope - Burris is generally pretty good about making things right, so you should be fine (even though the delay in getting to play with your toy sucks).

 

[KurtM]

Sounds to me like the front mounting point isn't allowing your ring to sit all the way flat into the notch in the flat top. Who's rings?? Many types of rings will fit a Weaver slot, but are just a bit too big to fit a Picatiny rail slot, and if the front slot is tight to spec and the the ring big it won't fit all the way down, but it will tighten up, causing hard to zero issues.

 

[tjones96761]

Sounds to me like the front mounting point isn't allowing your ring to sit all the way flat into the notch in the flat top. Who's rings??

Actual Weaver rings, manufactured by Weaver.

 

[mr ed]

+1 to KurtM
The rings are the problem
I just mounted a scope on a marlin and used an older base(as I had a drawer full) and went to walmart and picked up a new set of rings.
they didn't want to set in the grooves either.
couple passes with a file and they fit fine. only a few thousandths off, but enough to screw you up.

 

[doctorjj]

Sounds to me like the front mounting point isn't allowing your ring to sit all the way flat into the notch in the flat top. Who's rings?? Many types of rings will fit a Weaver slot, but are just a bit too big to fit a Picatiny rail slot, and if the front slot is tight to spec and the the ring big it won't fit all the way down, but it will tighten up, causing hard to zero issues.

I bet you're right about the rings being the culprit but wouldn't it be the back ring not seating causing it to shoot high?

 

[KurtM]

Uhhhh...Yeah Like DrJJ said. He is right, the last time I had this problem brough to me it was the front and Yes in that instance it was indeed low...but hey I had a 50/50 chance