I have an ACOG on my Colt 6940 and an Aimpoint on my LMT defender. Both 5.56 guns. If I switched out optics, on average how far off would one optic be from another. Is there any data on this? I guess I could get a general look via my BUIS?
Different guns even of the exact same make will vary. You must sight your optic in for the gun its going to be used on.
Pat
I thinkthat obvious. I was trying to find out what the average variance might be. 6 inches, 14 inches 24 inches. So in QCB, in a pinch could you swop out . I have read that you can use your Aimpoint , minus the red dot, ideal NO, but better than hip firing. Maybe there is no guesstimate, too much variance?
Just from swapping out optics I would say there is too much variance.
pat
If you had quality repeatable zero mounts for each optic and you zero’d each optic on the same weapon, same mounting point each time, your results would be very good at CQB ranges.
Now if each optic was zero’d on separate uppers, I don’t think you could give a reasonable estimate as to POA / POI when switching from weapon to weapon as a generalization of all uppers. At best you could use quality repeatable zero mounts and making sure to mount them in the same spot on each weapon try it out for yourself and determine where you are on paper. But to give a guesstimation without actually shooting the weapons, is difficult.
Now if I had to guess, I would think that within 5-7 yards, results would be within combat effective accuracy with a good mil-spec upper, but there is no way to assure that without testing it out.
Would I ever rely on such a thing without testing? Nope. I used to run an ACOG and an EoTech depending on my needs. Even with repeatable mounts on both, I could have zero’d both for the same weapon, however I chose to leave each optic mounted on its own dedicated upper and swapped uppers to fit what I was doing. While not “ideal” for each optic, I could still use either in a pinch up close or at a distance.
When I first started shooting I had an M&P 15 and a Bushmaster and I did the same thing where I had a scope on one and a red dot on the other. When I swapped them the groups by almost 5 inches or more. The groups even moved roughly 2" just moving the scope up and down the rail system. I don’t think there is a science to it but if you could zero your dots for each system and mark those zeroes and then have a consistent mounting technique you might be able to do an accurate swap and not have a huge change of POA/POI.
EOTech even says that removing and replacing the optic on the same place even with the ARMs mount will alter the POI by up to 1 MOA.
Most manufacturing tolerances are tight but when you think that a 20 MOA scope mount is only 1/3 of 1 degree in a rise, it kind of puts things into perspective.
If a swapped mount/optic is only 1/3 of a degree off from one gun to another that is still a 20" difference at 100 yards.
(1/3) of 1 degree = 0.00581776417 which seems rather insignificant, but try swapping it yourself at the range. You can always re-zero things before you leave the range.
In CQB you could swap out the optics and, without zeroing, reasonably expect to hit most bad guys, assuming that they were presenting a large frontal target and you were aiming center of mass. You probably wouldn’t hit them center of mass, but at CQB ranges you’ll probably hit them somewhereIf they were behind cover or had a hostage, you’d be better off using BUIS.
Swap them and see. It could be a few inches to more than a foot at 100. This would also be a good way to find out if they return to zero on the original rifles.
A few days ago, I moved an RDS from one 16" carbine to another. It was about -6" elevation, +1"R windage, at 25yds on the second gun. Sample size of one, but pretty consistent with my recollection of other swaps, too.
Quality guns, with rails true to spec, and quality mounts, are likely to produce less deviation than those that are not.
How about same gun, different power scopes, each with quality QD mounts? DMS-1 for close-medium range pig hunting, and a Elite 3200 4-12 for Mouflon or deer. Each scope zeroed on a MTS upper.
I could tell you it’s usually 4-inches high on one and 3.5-inches to the left. But I’d be full of shit (which may be why my eyes are brown).
There is no such standard when switching optics between rifles. You might luck out once in a while were the shift might be minimal between two rifles. But the only way you can obtain this data is trial and error.
In essence, all the right answers are going to cost money (another optic or another upper), as each upper receiver is going to have a unique relationship with that barrel’s POI, and when zeroing a rifle all one is doing is adjusting the optic once mounted on the upper receiver to have a POA that coincides with that existing POI of the upper.
For top notch uppers, the POI could be within 5MOA, but without testing, such an unknown quantity isn’t recommended. Using the BUIS to adjust the red dot and see how far off you are might be a viable strategy, but why install an optic that isn’t fully capable of making hits? That seems silly, just run the uppers separately - unless you have some case where the uppers couldn’t be used for distinct roles.