This rifle is going to have either a 16 or 18 inch mid-length barrel, and is intended to fill the gap between my 20" AR10A4 with TA11C and 16" Carbine with EoTech. My two choices are the TA31 and whatever the number for the compact ACOG 2x red triangle.
I think in general the TA31 has more advantages. It has basically the same reticle as my TA11C, which I would prefer over the triangle. It can also use the outstanding LaRue mount (The one for the compact is too low for my taste)
Unfortunately, I will be using 75 grain ammo, which doesn't fit the BDC too well, so I'd probably just use a 50 yard center of donut zero to get an IBZ like trajectory and not worry about ranges past ~250 yards. The alternative is a much higher zero, that is really too high to about 300 yards, after which it is quite good.
My really big concern about the TA31 is eye relief. I'm worried that it will be very difficult to go between the short eye releif of the TA31 and the much more forgiving TA11. Does anyone do this regularly?
The 2x compact ACOGS have a similar eye relief to the TA11, but I'm not sold on the reticle. If not for size, I would probably just get another TA11C-- the .308 BDC matches the 75 grain OTM trajectory as well as anything and I would keep full familiarity-- but it is quite large for what I have in mind for this build.
I might suggest that you change your title to "Which of these 2 ACOGS should I get?", since you already have it narrowed down to those. That way, idiots like me who are too poor for an ACOG won't click on this thread hehe.
imo the ta31 would work and the ta31f or ta31a would be better.
the triangle tip would offer a more precise aiming point.
i have the ta31 and ta31f and have no problems with either reaching out but the ta31f is more precise/easier to shoot out further.
personally i would not consider the 2x on shorter accurate rifle. after shooting my newly acquired ta47r-2(2x triangle) its fast but not precise as the ta31 series. i have it mounted on my 9mm carbine.
the eye relief is not terrible but i do understand where youre coming from cause after shooting the ta31 line shooting the ta47 was a bit different but not horrible.
heres a pic of my ta31f and my ta47r-2
The 47-6 uses a 6.9moa dot, which is close (recticle size) to what the TA11 uses (4moa).
I too use a TA11 on my 308 and a TA31 on one of my AR15s.
Guess what my other has mounted? Yup, a 47-6 zeroed at 50 yrds.
I would think the 2x would fit nicely between your 1x Eotech and your 4x(ya, 3.5x, im rounding).
The eye relief is much better than TA31, and quick to pick up the bright yellow (for me).