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)
http://i26.photobucket.com/albums/c113/Starofire/AR15/fa7be853.jpg

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)?

[ucrt]

.

I use a T-1 on an ADM 1/3 Co-Witness mount. I tried an experiment once where I shot 5-shots at 50 yards removed the T-1, tapped it on the table, put it back on, shot 5-shots, took it off...until I did this 4 times shooting a total of 20-shotsfor a 1-3/4" group.

I think several thngs need to be taken into consideration:
- Set the lever to tighten as tight as possible. For my ADM, I put an soft Buna-N O-Ring under the nut to give it some springiness.
- Return to the same slot each time.
- MAke sure you mount is 100% on the receiver with no end over hanging. Get all the grip you can.
- As you mount the sight use your thumb to apply significant pressure to move the mount forward in the slot it is in as you tighten the mount screws or lever.
- If you mount screws on, torque the screws the same each time. For my scope mounts I use only my thumb and index finger to tighten as hard as I can. This get me about 25in/lb.

I've tried this technique with scope and RDS and have been pleasantly surprised they come back to zero.

.

[Robb Jensen]

So it's normal for the zero to shift after removal of the RDS? Yes. 0-50yds it's hard to notice at 200yds and 300yds I can easily notice.



I have heard of people who have pulled their Aimpoints off and put it right back on and it's same dead on.
Most don't shoot well enough to see the shift, much of the time it's masked by the lack of accuracy from the shooter.



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)? RTZ is marketing material.

[TehLlama]

Yes. 0-50yds it's hard to notice at 200yds and 300yds I can easily notice.

Most don't shoot well enough to see the shift, much of the time it's masked by the lack of accuracy from the shooter.

RTZ is marketing material.

Absolutely true - that said, I prefer RTZ mounts simply because if I do need to remove the optic, when I put it back on I'll at least be on paper to re-zero.

[ALCOAR]

I can only truly and definitively with supporting evidence if need be say that ADM Recon-x's, Scout-X, AD-B2(T1 mount) mounts will absolutely return my zero within 1-2" at the very most every single time...be it at 25m or 100m.

On paper with my precision based ARs @ 100yds I can pop a nxs on and off all day long and rtz to within 1"-2", and again I am being very generous on the 2".

So lets be clear on this, ADM's RTZ is NOT marketing material. Ive own a cpl. larue mounts but never tested them, let alone as thoroughly as I have over the years with my ADM glass mounts.

[JimT]

I have noticed lateral zero shift with my optic mounts at 100 yards. Impact shifts between distances from 0 - 50 yards are negligible. However, at 100 yards I have had to adjust my Aimpoints laterally by two clicks (~1") from time to time whenever the optics are removed.

The RTZ mounts that the Aimpoints sit on are manufactured by the two most prolific companies out there.

Optics get removed whenever my uppers receive deep cleanings, and I expect some shift in zero. Nature of the beast.

[Iraqgunz]

My ACOG is in an ADM mount. I have removed it, and then reinstalled and any shift was essentially a non issue.

[sabrefan]

"I am at the range zeroing Speer Gold Dot 64gr "

Off topic, but CTD has 64 gr. gold dot from BVAC at $9.40 a box. I bought 5 boxes and intend to buy more. They call it their "barrier" load. Don't know what you paid, but these are worth the money. I've inspected all rounds, shot 1 box and highly recommend them. Bought them for deer rounds but never got a chance to try them on anything but paper.