I have two different ARs, from two different manufacturers, and to get the flip up iron sights in both of them zeroed, I had to crank the rear sights all the way to the right to get to anything close to a zero.

I’m guessing the problem is me, and not two different ARs.

I think I’m holding a good sight picture: front sight post centered in the aperture, superimposed on the target at the 6 o’clock position, focus on the front sight with left eye (dominant) open and right side closed (I’m a lefty).

Any advice? Why would I shoot so far left and have to compensate so far to the right?

Thanks, Andy in VA

Do you wear RX glasses ?

could be parallax from looking through your glasses at an angle.

My first thought, since you’re left handed, is that you are either pulling the trigger left or otherwise your trigger hand is too tight and pulling left.

What is your setup and position when zeroing? Are you in a prone supported position? Rifle on a rest with a sandbag rear?

Have you tried not gripping the pistol grip and instead hold your hand like it’s a standard bolt action with less grip pressure, fingers barely gripping the grip?

If cheek pressure, I’d expect it to pull right since you’re left handed.

No glasses. Laser eye surgery a while back.

I was shooting seated at a bench with the rifle on a bipod shooting at a 25 yd target. I’ll try the lighter grip next time out. Thanks.

What brand of backup irons are on them?

Sounds to me that you have improper head position/cheek weld. If the sights are both "bottomed out" in the same position, i.e. far right, you need to move your head/cheek/ eyes to the left--somehow. Your cheek needs to be tight up against the butt stock. Maybe try tilting your head a little bit to the left. You might have the butt plate too high in your shoulder "socket".
Here's a way to check your position:
1) unload the rifle and remove the magazine
2) double check that the rifle AND chamber are empty
3) mechanically center the rear sight
4) check again that the rifle has no ammo in it
5) stand in front of a mirror (bathroom, hallway, etc), shoulder the rifle, and then aim at yourself in the mirror. You should be able to see where your aiming error is (head position, cheek weld, etc., etc.). Check that you don't have the rifle "canted" (not straight up and down) in any way.
Hope this helps you out some.
Keep us posted. Good luck.

Jon

A canted sight base or rail would cause it too.

Troy Industries, with the Tritium.

Thank you! Great advice. I’m betting this is part of it. And as always, safety is always first and never last.