I plan to mount it to a 20" upper and shoot M193.  Perfect so far.

Does the donut reticle work when mounted to a flat top rather that a carry handle?  I know this isn't "suggested" but I'm wondering if anyone has tried to make this work.  Can it even be sighted in properly?

Or maybe I should just keep trolling around for a TA31F and not pay attention to all the donuts that keep coming up on the EE.

Read this:The Big ACOG BDC Chart.  It shows the different adjustments for ACOGs that are not "optimized".

Short answer: if you want to flat mount a TA31, it'll work fine; the compensation required is not large at all.

Gravy.  Within MOA for the BDC - not nuts-on as the 31F would be, but good enough for a shooter like me.

Quoted: Gravy.  Within MOA for the BDC - not nuts-on as the 31F would be, but good enough for a shooter like me.

Yep, close enough for combat accuracy

It really doesn't matter. Any way you cut it, you're going to have to experiment and learn some hold-offs from the BDC indications. Even if you use the exact ammo specified (not likely), in the exact mounting configuration specified for the reticle in question, if you change altitude or temperature from standard (highly likely) the BDC is going to be off from reality.

I use a TA-11 on a 20" flat top with 77 gr. ammo; a combination disimilar to anything Trijicon specifies. By shooting the gun to learn where the bullet actually goes, I'm good from 0 - 600 yards. Speaking of yards, you do know that the ACOG bdc's are calibrated for meters, right? Another problem...

Luck,

SD