TA33-8 on a 20” Flattop, will the BDC still Work?

Tactical Gear Optics & Mounts
1

I have a 20” Flattop that I want to use a TA33-8 on. I know these are calibrated for 14.5/16” barrel. Will the BDC markings still work as intended?

How far off would it be using 55gr and 62gr ammo?

2

I used M855 62gr as an example. I googled for the velocities out of the 3 lengths and got what you see below. All are sighted in at 100 yards with a bore to sight height of 3.0" and using a ballistic coefficient of .304. If any of my variables are wrong, someone let me know and I’ll rerun the numbers. I used the program “Point Blank.”

So, here is what you’d be looking at for bullet drop differences from those different length barrels.

So, the end result is that worst case I think you’d be looking at being off around 3" at 400 yards and a foot at 600 yards.

3

Thanks for running those, I had used a online calculator before but it was not working. I just googled “point blank” and downloaded it so I can run those numbers myself in the future.

4

Of course, glad to help. Definitely do try confirming those numbers. I just used the first things I found for bullet coefficient and velocities, so it could be a little off. Also, the 3.0 inches for bore to line of sight was based off just eyeballing my aimpoint in a larue mount with a tape measure, so it might be different with an acog.