I have two 4x acogs and of course they are great.
But I just noticed that 3.5x acogs have longer distance ballistic reticles. Like the one below for 3.5 x(which happens to be a .223 reticle). I am just wondering why a 3.5 x would have a longer distance reticle than a 4x.
3.5 x reticle for .223:
4x reticle for .223:
I don’t know the answer to your question.
I’ve owned a 5.5x TA55 ACOG and a 4x TA01 ACOG. My next one will be a TA11 3.5x. The TA11 has superior eye relief which is my major issue with ACOGs.
How far the BDC goes out isn’t the most relevant - unless you’ve got an FA weapon, running an ACOG beyond 600m doesn’t make loads of sense (it will work, but using a mid-range fixed zoom optic with simple BDC to make shots with a .22 cal projectile past that range lends it seld better to area that point fire). Would work fantastic for a 249/IAR, but not that great in a semiauto carbine)
On paper, the TA11 is the least attractive in the line - but arguably it’s still their best optic if weight isn’t your primary concern. The 3.5x zoom compared to the 4x is plenty close, and having just spent a whole week bouncing a TA31 against my ocular orbit, I can really appreciate the eye relief gains the TA11 offers.