After reading The Big ACOG BDC Chart I'm a bit confused about which TA31 to purchase for a 14.5" bbl M4A3, firing M193 type (Q3131A) ammo, sitting on an ARMS #19s throw-lever mount.

5.56mm Carry-Handle BDCs All full size ACOGs for 5.56mm use this BDC with the exceptions noted below. It is designed around a 20" barrel firing M193 with the ACOG mounted in the carry handle. If you have one sight in according to your manual. For a Flattop 14.5" firing M193: Sight in per your manual but at 50yds (or sight in 1.5" high at 100m). You'll be high at 100; but virtually dead on until 600 where you'll be 12" low. --- (F-Series) This BDC is based on a 14.5" barrel firing M855 with the ACOG mounted to the receiver via a TA51 mount. If you have one of these, sight in according to manual.

In the F-Series part, no data is given for a 14.5" bbl firing M193 w/ a flattop reciever mount.  Is this ballistically close enough to the M855 out of the same config (which the -F was designed for) to count as the same?  Does the ARMS #19s affect this at all?

Is the regular TA31 more suited for my application than the more expensive TA31-F?

Thanks much.

Figure out which reticle you want first TA-31=Donut BAC/TA-31F= Chevron BAC.Either will work with your setup on a Arms #19S.The BDC's are just calibrated a little differently.The TA-31 being a Carry Handle Mounted BDC and the TA-31F being calibrated for flat Top configuration.I just posted on the Acog BDC chart for a TA-31 with Arms #19s with 77gr. out of a 20" barell.Hope this helps I just thought I would take a stab before the Experts showedup.Jm03  

You are right that I left out the stats for a 14.5" F-reticle shooting M193. I'll edit the post and add that.



You won't notice any difference greater than 0.5" out to 300m. After that the M193 starts to lose momentum quick and will start impacting lower than the BDC. At 400m you are only 3" low (still within MOA) but by 500m you are 9" low and by 550m you are over a foot low (15") off the BDC.



Not for any practical purpose. If you are measuring fractions of an inch past 300 then it affects it.