My H1/LT660 is shifting with removal of sight

[298436]

Heylo,

I am at the range zeroing Speer Gold Dot 64gr (thanks C4I for having it) and I take it off to zero my BUIS at 50yds.

I put the H-1 and LT660 back on the flattop and the zero is off. By a lot. A couple of inches at 50yds.

What gives? My four screws securing the H1 to the LT660 are loctited, the securing lever is snug and doesn't wobble.

Is this to be expected?

[ALCOAR]

Still trying to think what could make a 100% RTZ mount like a larue not RTZ and esp. if it's by a large margin.

On another note...why not co wit. and then you would have no need to remove your H1 once it is sighted in....you just adjust your irons to the sighted in H1/reddot.

Did you mount the H1 on the return in the same location t-mark wise as before?

[spamsammich]

please be more specific, are you off in windage or elevation?

[Iraqgunz]

I agree with Trident. Set up the BUIS so that you don't need to remove the sight unless necessary.

Can I assume that you are also using the same ammo when you zero as well?

You could possibly have a defective mount assuming that all the other variables are constant.

[Robb Jensen]

I'm a bit old school. If I remove a QD mount after zeroing I expect a shift. I expect a shift regardless of who makes the mount. Even the best ones out there will have some shift. Most of the time one wouldn't see the shift if using a red dot non-magnified optic. But if this were to happen on a highly magnified optic with a precision rifle the shift could be very measurable at distance.

This is why I don't remove my optics after zeroing if I don't plan on check the zero again. Don't remove the optic and it won't shift.

[Dos Cylindros]

I also agree with Robb. I will add, to make sure you check that you are returning the mount to the same rail slot each time.

[snappy]

Did you adjust the tension of the levers via the bolt on top of the lever mechanism at any point in zeroing the process?

[ST911]

What gun (rails built to spec)? Mount in same location?

[298436]

1) Mount in same location yes. Pretty much as far as I can go with it (I'm not getting a cantilever mount). Spikes upper. (And I wish I'd gone with a BCM lightweight 16" mid, but they weren't in stock at the time: especially since Spikes don't clamp their barrels when they torque the barrel nut)


2) Lever tension was never adjusted by me. Felt snug and fine from the factory.

3) Windage and/or elevation. It's wierd.

4) I won't do absolute co-witness. I am only doing the zero without to get a more accurate zero with my BUIS since the A2 front sight post is a bit too thick to see our small targets at 200 to do a confirm zero.

[298436]

So it's normal for the zero to shift after removal of the RDS?

I have heard of people who have pulled their Aimpoints off and put it right back on and it's same dead on.

Or maybe it's an urban legend? Friend of a wives' tale that she told him? A fantasy report? Gunwriter's words (which he probably just picked it up, looked at it, and went back to the keyboard and wrote elatedly)?