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Page AR-15 » Optics, Mounts, and Sights
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Posted: 9/18/2023 7:31:37 AM EDT
I'm replacing the RDSs on two 5.56 ARs after discovering I've had astigmatism for 15 years and my eye doctor never mentioned it once. My now-previous eye doctor, I should add.

Is there anything special, secret, hidden, or not obvious I should know about installing or sighting them that's unique to Prism sights, please? It seems straight-forward but with all the expertise here and my near-total lack of experience with modern optics, I thought it would be a good idea to check.

Primary Arms SLx 1x Micro Prism Sight Illuminated ACSS Cyclops Gen II Reticle
Primary Arms SLx Gen III 3x 32mm Prism Scope Illuminated ACSS-5.56-CQB-M2 Reticle

Thanks!
Link Posted: 9/18/2023 8:19:27 AM EDT
[#1]
A good knock or two after zeroing can't hurt. We used to do that to our RCOs. Sometimes the calibrations could get 'hung up'.
Link Posted: 9/18/2023 6:22:33 PM EDT
[#2]
Just remember to adjust the rear diopter properly to your eyes and they say you shoot.  If you wear glasses, it can and probably will be different from if you wear non-rx safety glasses for shooting.

As for astig, probably 80%+ of people have it, if not more. I’d venture 90% is likely. Anytime you have a cyl correction on a RX it’s an astigmatism.
Link Posted: 9/18/2023 7:09:12 PM EDT
[#3]
I've had a lot of them and my favorite so far is the 2x GLX.
Link Posted: 9/18/2023 7:52:25 PM EDT
[#4]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
A good knock or two after zeroing can't hurt. We used to do that to our RCOs. Sometimes the calibrations could get 'hung up'.
View Quote

Smack the turrets after each adjustment to make sure there is no backlash and the adjustment is made.
Link Posted: 9/19/2023 6:25:47 AM EDT
[#5]
If you zero the irons with a 1x prism off the gun, that does not mean the irons are zeroed while cowitnessing through the prism.

Also, perfectly zeroing with a magnifier does not mean that you are perfectly zeroed without a magnifier.

If you zero the irons while cowitnessed and zero the optic with magnifier on, the differences will probably be minimal enough you won't notice a difference in most use cases.
Link Posted: 9/19/2023 6:59:29 AM EDT
[#6]
OP, I'm far from an expert, but I made the switch on my primary from an Aimpoint C3 (older model) to the PA 1x, as well as a 3x and 5x.

Compared to the Aimpoint, the 1x has a touch of parallax when viewing through the edge of the optic window.  Far from a deal breaker but it's there.  If you decide to go with a magnifier, adjust the diopter on the 1x first, and then magnifier.  As an aside, I use the magnifier ahead of the 1x vs behind it.  I haven't experienced a limitation with eye relief on the 1x at any position where my head is along the stock.

On the 3x/5x, I luv the 3x and like the 5x.  For the 3x, for me as long as the illumination is on high, occluded shooting works decently for close in.

Good luck in your quest.
Link Posted: 9/19/2023 8:23:16 AM EDT
[#7]
They have an eye relief. Long, but still a thing.
Link Posted: 9/19/2023 10:44:51 AM EDT
[#8]
You will have clearer glass than an Aimpoint but you will now have a little bit of fish eye if you move your eye around. It doesn’t impact function but it’s there.

Don’t mount it way forward like you would a red dot unless you have to. Eye relief is like 3 feet before you can’t shoot with it, but you will see the edges of the prism starting at about 6 inches. It’s just a very small amount with absolutely no impact on function if you must, but I run mine forward of my rear iron and there’s no field of view loss at all.

The 3X is my favorite.
Link Posted: 9/20/2023 4:48:53 AM EDT
[#9]
Thanks for the information and tips, everybody. You've been a big help. New sights arrive today, install tonight, range tomorrow.
Link Posted: 9/21/2023 8:02:31 AM EDT
[#10]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
If you zero the irons with a 1x prism off the gun, that does not mean the irons are zeroed while cowitnessing through the prism.

Also, perfectly zeroing with a magnifier does not mean that you are perfectly zeroed without a magnifier.

If you zero the irons while cowitnessed and zero the optic with magnifier on, the differences will probably be minimal enough you won't notice a difference in most use cases.
View Quote


I think I get all of this. Unlike an RDS, the reticle is fixed and won't move down to the iron front site as it will on a red dot, right? If I use a 1/3 co-witness- height mount under the prism and sight through the reticle and front post, my sighting will be 1/3 off.

It would seem that the solution is to retain the rear pop-up sight, making sure it can be used through the prism, and sight in both sights independently?

Thank you!
Link Posted: 9/21/2023 8:07:53 AM EDT
[#11]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
You will have clearer glass than an Aimpoint but you will now have a little bit of fish eye if you move your eye around. It doesn’t impact function but it’s there.

Don’t mount it way forward like you would a red dot unless you have to. Eye relief is like 3 feet before you can’t shoot with it, but you will see the edges of the prism starting at about 6 inches. It’s just a very small amount with absolutely no impact on function if you must, but I run mine forward of my rear iron and there’s no field of view loss at all.

The 3X is my favorite.
View Quote


Sounds good. I prefer them closer rather than farther so that's a good match. I went from no AR-15s to four AR-15s in the blink of an eye this Spring and I'm trying to be as consistent as possible with my head placement across all of them. The 3x is going on my coyote shooter. I'm anxious to get it into service. The cold will be chasing the 'yotes out of the mountains soon.
Link Posted: 9/21/2023 8:08:42 AM EDT
[#12]
Diopters and turret smacks. Got it. Thanks!
Link Posted: 9/21/2023 8:37:44 AM EDT
[#13]
I test-fit it as far back as I could and this is the result. The pop-up MBUSs are in perfect vertical alignment with the reticle as far as I can tell with my eye. They are off-center horizontally but not so far that they're outside adjustment range.

Is it too close to the rear MBIU?

Normal use: Backup sights folded down, sight through prism.
Prism failure use: Backup sights up, sight using iron sights, through prism glass.
Prism destruction use: Remove prism, sight using iron sights.

I'm going to go ahead and torque it down where it is. I'll be taking it to the range in about four hours, so if you see something I need to fix before then, please let me know. I'll probably have my club's armorer look at too when I get there. Not so much because I'm worried about it ... he's a nice guy and every time I show him something, we drink some coffee together and I learn something new from him.

Link Posted: 9/21/2023 9:30:28 AM EDT
[#14]
Out with the old and in with the new. I stuck a Venom Vortex RDS onto the rail that came attached to the stop of the sight. It was on a quick-attack mount, so I just slapped it on. Not sure how I feel about it. If I do decide to shoot with it this way, I'll take off the riser mount and mount it on top on a flat base. I know I can hit a target at 25 yards with this red dot, even with my astigmatism. The "dot" may be the size of a fist at 25 yards but that's good enough at that range. So even though I'm not planning to use it for close-up self-defense, it would be nice to be able to do so if needed.

The MBIUs are useless. The front sight is all but invisible under magnification and the rear sight is so low, it's beneath the edge of the glass. I'm not sure if I'm worried about that with this rifle, though. Especially if I keep the red-blob sight on it.



Link Posted: 9/21/2023 10:01:57 AM EDT
[#15]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I test-fit it as far back as I could and this is the result. The pop-up MBUSs are in perfect vertical alignment with the reticle as far as I can tell with my eye. They are off-center horizontally but not so far that they're outside adjustment range.

Is it too close to the rear MBIU?

Normal use: Backup sights folded down, sight through prism.
Prism failure use: Backup sights up, sight using iron sights, through prism glass.
Prism destruction use: Remove prism, sight using iron sights.

https://www.ar15.com/media/mediaFiles/582146/SLx-1-1-2961203.jpg
View Quote

If you moved the BUIS forward for charging handle slingshot clearance, cool. I recommend having the big aperture ready to use, especially when further forward. Otherwise move it back a slot or two.
Link Posted: 9/21/2023 10:03:08 AM EDT
[#16]
Issues with nightvision compatibility
Link Posted: 9/21/2023 10:07:40 AM EDT
[#17]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Out with the old and in with the new. I stuck a Venom Vortex RDS onto the rail that came attached to the stop of the sight. It was on a quick-attack mount, so I just slapped it on. Not sure how I feel about it. If I do decide to shoot with it this way, I'll take off the riser mount and mount it on top on a flat base. I know I can hit a target at 25 yards with this red dot, even with my astigmatism. The "dot" may be the size of a fist at 25 yards but that's good enough at that range. So even though I'm not planning to use it for close-up self-defense, it would be nice to be able to do so if needed.

The MBIUs are useless. The front sight is all but invisible under magnification and the rear sight is so low, it's beneath the edge of the glass. I'm not sure if I'm worried about that with this rifle, though. Especially if I keep the red-blob sight on it.

https://www.ar15.com/media/mediaFiles/582146/SLx-3-1-2961259.jpg

https://www.ar15.com/media/mediaFiles/582146/SLx-3-2-2961258.jpg
View Quote
Yep. Irons don't co-witness with magnified sights, especially when the sight heights differ. My scopes get QD mounts.
Link Posted: 9/21/2023 1:54:11 PM EDT
[#18]
Adjustments complete. I'm off to the range.

Thanks!



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AR Sponsor: bravocompany
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