55gr and 62gr trajectories won't differ by more than a couple inches (absolute MAX) at any range you're gonna find the ACOG useful.

Save some money and shoot 55gr M193-spec.

From The Big ACOG BDC Chart tacked in the optics section
www.ar15.com/forums/topic.html?b=3&f=18&t=152794


62gr. 5.56mm Flattop BDC

ACOGS that use this BDC are the:
TA01NSN, TA31F, TA11F, TA11F-A

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.

Stats used to figure BDC baseline:
M855 traveling at 2,970fps with a BC of .304 and a height over bore of 2.5"

For a Carry Handle 20" firing either M193 or M855 - you're screwed. There is no way you will match the BDC close enough to make it useful. You'll just have to learn where the rounds strike on your BDC and adjust.

For a Flattop 20" firing M193:
Sight in per your manual. You'll be within MOA of your BDC.

For a Carry Handle 16" or 14.5" firing M193:
Sight in .25" low at 100m. You'll be an 1" at 200, 2" high at 300 and 400 and then within MOA out to 600.

For a Flattop 16" firing M193:
Sight in at 100 per your manual. You'll be a half-inch high at 300, dead on at all other ranges until 500. At 500, the M193 starts losing juice fast on this trajectory, you'll be 2" low at 500 and 9" low by 600.

For a Flattop 14.5" firing M193:
Sight in at 100 per your manual. You'll be a half inch low at 300, 3" low at 400, 9" low at 500 and 15" low by 550. Once again, the 55gr loses gas fast past 300, so there isn't much you can do here without making your near zero absurdly high.

For a Flattop 16" firing M855:
Sight in per your manual. If you can notice this difference on the BDC you don't need to be asking me for advice.

For a Carry Handle 16" firing M855:
Sight in 0.1" high at 100 - this will give you a profile very close to the carry handle shooting M193.

EDITED TO ADD Hornady 75gr OTM Data

For a Carry Handle 20" firing 75gr OTM @2750fps
Sight in at 100 per manual. You'll be very close to the BDC with the maximum deviation being 4" high at 600

For a Flattop 20" firing 75gr OTM
Sight in at 100 per manual. You'll be on the low side of the BDC instead of the high side but within 2" or less all the way out to 600.

For a Carry Handle 16" firing 75gr OTM
Sight in 0.4" at 100 (or sight in normally at 75). You'll be a half inch high at 200, dead on at 300 and within MOA to 600.

For a Flattop 16" firing 75gr OTM
Sight in 1.1" high at 100. You'll be 1" high at 200, dead on at 300 and MOA until 600 where you will be 7" lower than the BDC.



Hope that helps you.

Dont hesitate to ask if you have any other questions!