Can some one tell me what model I need for the must haves I want? The website isn’t as clear about which reticle is calibrated for what. I have an older m4a1 colt socom that has the 16 inch barrel. Now I know I’ll probably just get one calibrated for the 14.5 inch which should be close enough. I want the 3.5x35 acog led with either the cross hair or donut reticle. These seem nice as can install a rmr mount in the forward topside position. I plan to run m855 out of this setup as my gun seems to really like it even with the matech backup sights at long distance. Which model should I run for this loading to be calibrated with the reticle? I’ll settle for the 4x32 led version if I have too. Thanks in advance.

The donut reticle is useless for precision, it works fine for CQB style shooting. The ACOG 3.5x crosshairs are the best available in any ACOG scope. They eliminated the 200-meter hash line giving the user an uncluttered view of the 100-meter crosshairs.

https://www.ar15.com/forums/AR-15/Optics-Mounts-and-Sights/18/

I’ve used a TA31F on 14.5, 16, and currently 20” rifles with great success. 4x fiber optic and she is CLEAR and magnificent.

I've got a TA11 (3.5x) with green crosshairs, would go with the same if I had to do it over

Is your crosshairs calibrated for m855?

Just says .223 BDC https://www.trijicon.com/products/details/ta11j

I’m thinking ta02 or the ta110 with crosshair. How’s the eye relief in most situations? Is it really that bad running the 4x32 compared to the 3.5 x35? I’m going to end up running the rmr mount in the forward position for up close work anyway.

I only experience the ta31 and ta01 models in 4x. For the fiber optics ones you can do something called Bidon Aiming concept up close. It’s essentially an occulted eye system where you’re using your non dominant eye to “see” and your dominant eye is painting the reticle over the target. It works reasonably well in close quarters but requires some concentration from my experience.

The problem I have with acog is not the eye relief per se but when I had a piggy back rmr it was just right to hit to top of my helmet or eye pro and it was annoying. Never liked acogs and when I got my personal one I liked the 4x concept and went with a elcan that’s so much better. It has a short eye relief but it’s made well enough so you’re not too close and while I don’t have a helmet anymore it’s not hitting my eye pro.

Wish I had a picture of my old eye pro as they had dings all over from where the acog hit.

Bindon Aiming Concept

ACOG’s (except a couple models listed below) use a prism geometry that doesn’t match the size of the objective lens. I’ll use my TA50 for example as I’ve actually measured it.

Peak FOV is at 2” closely matching the listed eye relief.

Peak eye box (side to side exit pupil forgiveness) is at about 3.5”.

If you run them at peak FOV you’re going to have a short shitty eye box. If you run them at peak eye box you’re going to have FOV loss due to objective lens shadowing. I used to think this was bad engineering but have come to the conclusion it was on purpose. You have a fast BAC from the slightly reduced FOV with lots of eye box forgiveness for a combat optic. Then you can choke up on it for peak visuals when you need/want it.

Models like the TA11 and TA33 were designed to bypass this feature for the people who can’t get around the psychology of using an optic anywhere but peak FOV. The TA33 is literally just a TA50 with a blinder to reduce the FOV to match the peak eye box. As such, they are what they are and I personally dislike the TA11’s eye box despite it being more forgiving (only) at peak FOV.

ETA: To be fair, I haven’t tried this with a TA31 before connecting the dots on my TA50, but you can find loads of feedback from people saying the TA31 has a crazy long eye box despite shadowing, so I suspect the same but can’t verify just yet.

This makes so much sense. Is the TA50's FOV larger than listed on Trijicon's website? Their numbers aren't always correct, and 25ish ft at 100yd is pretty small for a 3x optic.


I want to love the TA33 so badly but can't deal with the drinking straw FOV, and you tell me they did it on purpose? If this is true it makes me hate Trijicon even more.

The quoted 25 feet is likely correct, but that’s just guessing. With how compact the optic is it feels bigger though. I know that doesn’t make sense and I have no logical explanation for it.

And yep, they reduced the field of view by pushing the objective further away. If you look through a TA50 at the TA33’s peak eye relief, the field of view is probably about the same. The TA50 just won’t have the clean edge and will be shadowing instead.

I wish I understood prism optic design, or knew of a calculator that I could play with to design my perfect prism optic, but it would probably just make me even more frustrated with Trijicon
I have a pair of 8x32 prism binoculars and IIRC they have a linear FOV of 40ft at 100yd. I know they're binoculars and not a rifle scope, but the construction and design principles should overlap significantly with an ACOG, so I'm a little cheesed that the TA33, which is this close to perfect, is handicapped with an abysmal FOV, especially at such a low magnification.
But that doesn't bother some people, and they love the TA33 and can't stand the TA31, which I think is a great optic.

I may have to check out the TA50, I'd dismissed it previously but it sounds like it's worth a look.

I'd just be happy with a ruggedized diopter, but I guess that's what BCGs are for.

If you want peak FOV it might not be the best option. The eye box is massive but only outside of the peak FOV. It’s like a TA33 that you can push forward to have better FOV, but the eye box really isn’t that good there.

For me, the TA50 is without a doubt my favorite AR optic set up I’ve ever tried with the RMR on top. As lightweight as you can get and lightning fast.

Attached File

The TA50 may be my favorite ACOG, followed by the TA31.
Definitely check out the TA50.

The battery powered versions are nice, but noticeably heavier. They do have better RMR position at the front.  Having had both the 4x and 3.5x crosshair version in both battery and FO, TA11 FO no question.  The 11s are just so nice to look through, the reticle is better (finer, no 200m line), the image quality is better, the exit pupil is better, only downside "only" 3.5x and heavier.  The 31s have that big fov and less weight, but everything else is compromised.  I just don't enjoy using them, when looking through a Ta11 they're just so nice.  The fiber optic Ta11 with the crosshair is my favorite ACOG, TA31 with crosshair is my least favorite ha. Ta110 + RMR is pretty chunky like 23oz., the fiber optic with something like a Geissele mount + rmr is 19.5 oz.  
The only reason to go 31 is less weight\bulk if you're walking up and down mountains.  Crosshair is calibrated for m4 14.5 barrel, so 16" +m855 should be pretty close.

Peak fov\pulling back with shadow for quick shots works great.. assuming your ACOG is optically centered when zeroed.  Many of them aren't (when pulling back from the scope, the image will quickly become a crescent moon with half of it greyed out.)  I've discussed this with Trijicon, they admit they don't care about eyebox or optical center, as long as the scope can be zeroed.  So if you're lucky and have a good one that's centered, pulling back for max shadowed fov works great.  If you have a few like I do where the eyebox is shifted really far to the right or up, Trijicon says "put your eye closer to the scope" and I can't use them like that