What are the chances one red dot will contain the same zero between two "mil spec" AR-15s?

I have a red dot on one AR, zeroed for 50yds ready to go.

New AR will be done this week, and was wondering if I can swap the same red dot (has a American Defense QD mount BTW) between both rifles until the budget allows for a second red dot?

Oh and BTW:

AR with red dot zeroed:
1:9 twist
16" Chrome Lined, heavy profile.

Newer AR I'm looking to use same red dot on:
1:7 twist
16" Chrome Lined, Government profile.

What are the chances one red dot will contain the same zero between two "mil spec" AR-15s?

I have a red dot on one AR, zeroed for 50yds ready to go.

New AR will be done this week, and was wondering if I can swap the same red dot (has a American Defense QD mount BTW) between both rifles until the budget allows for a second red dot?

Oh and BTW:

AR with red dot zeroed:
1:9 twist
16" Chrome Lined, heavy profile.

Newer AR I'm looking to use same red dot on:
1:7 twist
16" Chrome Lined, Government profile.

If you have BUIS on both, and both are mechanically zeroed at 50 yards without needing to adjust the sights, you have a good chance of the red dot being very close on both rifles.

"Mechanical zero" is when you center the rear sight and have the front sight in the center of it's highest/lowest positions.  If both rifles shoot dead center on mechanical zero, then I'd expect the red dot to keep its zero when moved between them.

Also, if you have to adjust the sights to hit the bull with BUIS, and the adjustments are the same for both rifles' sights, again, once the red dot is zeroed on one, it should have a good chance of being zeroed on both.

That's my theory.  I've never tried this, since I know just moving an optic can change the adjustments and could require re-zeroing even for the same rifle.

Or really close so it would only take a few rounds to find zero again...

Very slim. 

Just wait till you have funds to buy a second.

Very slim. 

That's what I would bet on. Way to much variance between tolerances in uppers and barrel fit to be zeroed. I guess it all depends on how close is good enough. Please post your results though.

I think that if you had two identical rifles, from the same production run, that the accuracy would be as good as possible given you were removing and reattaching an optic. For a red dot at 50 yards, probably completely acceptable.

For any other situation, I think the odds of you being happy with the results are pretty close to 0%.

But what does it hurt to try? And post some pictures of the results?

I've swapped red dots from one gun to another a few times and from what I've seen, the dot was never what I considered "on" for the second gun.  I guess it depends on what your expectations of the "usability" of the red dot on the second gun. 

IIRC, the dot was on paper with the second gun on first few shots at about 25 yards.  Don't recall how much they were off from what was zero on my gun though.  These were all "mil-spec" guns.  This was in a carbine class where I used the red dot on my second rifle and let another shooter borrow when they had problems with their dot.  In one class, it went on two different guns over the multi-day class.  In a later class, it went on another gun.  I'm trying to remember how much I had to adjust them back when I put the dot back on my gun, but I don't remember.  I want to say it was within about 6" at 50 yards though.  But then, I reconfirm zero when I put the same optic back on the same gun, even if the QD mount is supposed to be RTZ.

I saw a device that mounts to the rifle and has its' own adjustments so you can have your optic zeroed to one rifle, then simply move it to the other with the device so it keeps the zero.  Let me go find it for ya.

Reading the comments yeah.. not even gonna bother with trying it out and no they will not be from the same manufacturer. One is a Colt and the other without an optic right now is BCM.

Will just wait a month or two before I can get a second dedicated optic for the other AR.

I saw a device that mounts to the rifle and has its' own adjustments so you can have your optic zeroed to one rifle, then simply move it to the other with the device so it keeps the zero.  Let me go find buy it for ya.

Thanks! 

Reading the comments yeah.. not even gonna bother with trying it out and no they will not be from the same manufacturer. One is a Colt and the other without an optic right now is BCM.

Will just wait a month or two before I can get a second dedicated optic for the other AR.

That sounds like a good plan. 

Just curious, what would you have considered an acceptable zero when putting the dot on the second gun? 

Found it!!!!! I know the product was under development, not sure where it's at now or how much it costs.

Found it!!!!! I know the product was under development, not sure where it's at now or how much it costs.

Ahh, Garand Thumb.  I like that guy's videos.   

Thanks! 
That sounds like a good plan. 

Just curious, what would you have considered an acceptable zero when putting the dot on the second gun?

Honestly, I can’t really say what I would have “accepted” unless I tried it. I COULD give it a shot for the time being to see that it ends up being.

But if I had to say, it would need to be dead on. I was verifying a 50yd zero with a 10yd target – drawing 2 dots on paper 1.9” apart (one on top the other). Top dot is POA, bottom is my grouping. So I imagine at 10 yards vs a true 50yd target, I’d need it to be dead on.

Found it!!!!! I know the product was under development, not sure where it's at now or how much it costs.

OH THIS IS NOT GOOD AT ALL.

It WAS available on Indiegogo funding BUT: This campaign has been closed by Trust and Safety due to a violation of our Terms of Use. The campaign will no longer be accepting contributions, and the Campaign Owners no longer have access to the campaign.

But even then I don't know if I'd want to mess around with one as it looks like it's just going to add height and Im already using a Lower 1/3rd QD mount. Plus with the cost, I might as well just wait for the second optic.

Thanks tho.

A red dot on 2 ar15 rifles can work with a QD.  You just have to record the difference in the number of clicks, elevation/windage, between the rifles and adjust accordingly when you switch.  Assuming you have a good quality optic and mount.

its easy to check at home after first zeroing both rifles irons at the range.
2nd step is install red dot on preferred picatinny slot and match the dot to the irons zero.
3rd switch the red dot to the new rifle, and put it in the same picatinny slot you used. see how far off the zero is. if youre lucky it may be close enough for you to plink with but i kinda doubt it.

you could then try moving the red dot forward or backward one picatinny slot and see if that puts it closer,  whichever slot is the closet you then make micro adjustments and take note of how much you adjusted it so you could then swap it back and forth and make your adjustments.

A red dot on 2 ar15 rifles can work with a QD.  You just have to record the difference in the number of clicks, elevation/windage, between the rifles and adjust accordingly when you switch.  Assuming you have a good quality optic and mount.

yeah the quality of the qd mount and the optics tracking adjustments are important.

A red dot on 2 ar15 rifles can work with a QD.  You just have to record the difference in the number of clicks, elevation/windage, between the rifles and adjust accordingly when you switch.  Assuming you have a good quality optic and mount.

I think you have to think about this from a "worst case" scenario where you're forced to use this rifle and red dot to shoot an intruder because you're in fear for your life.  You willing to trust your life on this?    I second what WTFShane said and get a second red dot optic for your new rifle.

I think you have to think about this from a "worst case" scenario where you're forced to use this rifle and red dot to shoot an intruder because you're in fear for your life.  You willing to trust your life on this?    I second what WTFShane said and get a second red dot optic for your new rifle.

use BUIS

use BUIS

Ren - read the OG post by the auth.  He's asking about moving a red dot between two different rifles...not about BUIS.