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Posted: 9/21/2004 7:02:12 AM EDT
Using the same upper, and a 22lr conversion unit, how do you guys switch back and forth with your zero. I have an EOTech and an ARMS #40. I don't think the EOTech's are very "repeatable" so I think "comeups" are out for that. And the ARMS 40 doesn't have elevation adjustments.
I do have an extra A2 type rear BUIS, so I might just zero that for elevation with the range wheel and switch it for the ARMS when I'm shooting 22lr. It would be better if I could zero the 0 range setting on the wheel for like 50 yards, and then raise the rear sight via the wheel for longer range 22 shooting. (If somebody knows how to do that without changing the front sight, that would be great.)
Let's hear your solutions.
Link Posted: 9/21/2004 2:08:15 PM EDT
For just plinking cans and stuff at 50yds, I don't re-zero; there's not enough of a difference to matter. If I was going for accuracy, I'd probably use something different since the conversion in my 16" bushy carbine won't do much better than about 2" at 50 yds anyway.
Link Posted: 9/21/2004 3:12:09 PM EDT
+1 on what ChiefPilot said, I find zeros on the two are practically identical at 50 yards.

If you need more than that, consider a second cheap sight for the .22, since it sounds like you have a flattop. Good used 3-9X scopes are available at gun shows for $35 or less. Walmart has a cheap chinese airgun 3-9X scope--airgun rated actually means it can handle MORE recoil than a standard scope. I've used one for thousands and thousands of rounds of .22. It's also about $30. Walmart also sells a cheap BSA red dot sight for about $32 that's also working just fine on my .22 LR upper.
Link Posted: 9/21/2004 5:33:43 PM EDT
Thanks for the replies so far. I'm using 60gr Aguila SSS ammo, since it's the only ammo that is reliable in my conversion. This ammo has a parabolic trajectory due to its low velocity. POI difference at 50 yards is 5.5 inches low. At 25 yards, it's about 2.5 inches low. Precision is excellent. I have the EOTech zeroed at 100yds with 5.56 ammo. If I re-zero the EOTech to 50yards, that will raise my POI a bit, but I don't want to change my 5.56 zero if I can help it.
I wanted to have a more precise system to deal with groundhogs and such, at ranges to 100yards or better, without the noise of 5.56.
Link Posted: 9/30/2004 3:42:34 PM EDT
It's been a while since I've shot the .22 conversion at 50 yards, but as I recall the difference between my 50-yard M193 zero and a 50-yard zero for regular High-Vel .22s is quite a bit. Something like 22 clicks on the scope. I'm sure it'd be more for the 60gr SSS. I shoot the .22 conversion mostly at 25yds with a detachable handle and the 25-yard setting for it is pretty close to the 25-yard setting for the .223s, but that's I think 7 MOA up from the 50-yard setting and 8 MOA up from the 100-yard setting.

Not too long ago I ran some trajectory charts on a thread for someone asking about the difference in POI for the different rounds, but I can't seem to find the thread right now. I think it was in AR Discussions. I used the JBM Ballistic Calculator which let me put in the .223 info and zero range then I recorded the Elevation angle (the effective "sight setting") and ran it again with the .22LR info and that angle to see where it would go if I didn't change the sights. IIRC the .22LR shot low at all distances, but I don't recall how much.

If I were you I'd zero the EOTech and ARMS#40 for 50 yards with your "combat" ammo and then see how far off the .22s are. I'm guessing it'll be too much for you. You should be able to find a setting on the A2-style BUIS that works for the .22LR w/o moving your front sight. The IBSZ page on the MD-AR15 site tells how to move the markings on the A2 elevation dial which might help get the correct setting at a number you can remember. The best way I can think of to handle the optics is to have 2 of them. I have a 2-7x on mine and I just picked up some cheap rings so I can put an old 4x I took off of a used .22 on it for shooting the .22LR instead of dialing in all of the clicks.
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