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.
Any thoughts?