Thoughts on IBZ-type sighting in for an ACOG?

[Doc Safari]

I just purchased a TA33R-8 ACOG with the red chevron reticle and BDC for 62-grain .223.

I haven't had a chance to go to the range yet, but I've been tossing around some thoughts in my head that I'd like to have the "best of both worlds" and find a way to sight in the optic more for CQB.

For those not familiar with the TA33R-8, the BDC is set so that the top of the chevron is 100 yards, the "dent" of the chevron is 50/200 yards, the top of the shaft of the arrow is 300 yards, and of course the horizontal marks down the shaft of the arrow are marked 400 yards, and the other marks are for further distances.

So, if you sight in the rifle at 25 yards your aiming point for 25/300 yards should be the top of the arrow shaft underneath the chevron.

If you sight in in for 50/200, you should use the concave part of the chevron.

Now, what would happen if you sighted it in for 50/200 at the TOP of the chevron? What does that do to all your other distances in relation to the parts of the chevron reticle?

Has anybody done this?

I'm wanting to have a way to pick up the target quickly out to about 200 yards, but I want some semblance of BDC calculations to still be relevant.

Thoughts?

[Failure2Stop]

100 zero beats 200 zero for close range work. Do what makes you happy, but you're losing capability by not using a 100 zero in an optic/reticle built around it.

From Tapatalk:
Jack Leuba
Knight's Armament Company: Military/Govt Product Liaison
F2S Consulting: Director of Shooting Stuff

[samuse]

I agree with Jack.

To add to that, the chevron is pretty small and it usually winds up getting used like an Aimpoint dot when you're in a hurry.

The difference between 100M and 200M with M855 from a 14.5" barrel is right around 2moa so it's not gonna hurt you too much to just be somewhere in the chevron up close (I never got along with using the crotch as an aimpoint and just held over at 200 anyway). What I do is zero the optic (TA31RCO) at 300M (using the 300M aimpoint) and confirm where it hits at 200, 100, 400, 500, or wherever I can.

I do that because the chevron is somewhat imprecise and close enough for 1-200M work. The game starts to change out at 300 and beyond where small errors become big misses. Tune the sight up for the long shots and the close shots will take care of themselves.

*Don't forget the ACOG is in Meters...

[steyrman13]

I agree with Jack.

To add to that, the chevron is pretty small and it usually winds up getting used like an Aimpoint dot when you're in a hurry.

The difference between 100M and 200M with M855 from a 14.5" barrel is right around 2moa so it's not gonna hurt you too much to just be somewhere in the chevron up close (I never got along with using the crotch as an aimpoint and just held over at 200 anyway). What I do is zero the optic (TA31RCO) at 300M (using the 300M aimpoint) and confirm where it hits at 200, 100, 400, 500, or wherever I can.

I do that because the chevron is somewhat imprecise and close enough for 1-200M work. The game starts to change out at 300 and beyond where small errors become big misses. Tune the sight up for the long shots and the close shots will take care of themselves.

*Don't forget the ACOG is in Meters...

THIS is really good advice!


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[Failure2Stop]

To add to that, the chevron is pretty small and it usually winds up getting used like an Aimpoint dot when you're in a hurry.

The difference between 100M and 200M with M855 from a 14.5" barrel is right around 2moa so it's not gonna hurt you too much to just be somewhere in the chevron up close (I never got along with using the crotch as an aimpoint and just held over at 200 anyway). What I do is zero the optic (TA31RCO) at 300M (using the 300M aimpoint) and confirm where it hits at 200, 100, 400, 500, or wherever I can.

I do that because the chevron is somewhat imprecise and close enough for 1-200M work. The game starts to change out at 300 and beyond where small errors become big misses. Tune the sight up for the long shots and the close shots will take care of themselves.

*Don't forget the ACOG is in Meters...

Yup.

The only reason to choose a 200 meter zero over a 100 meter zero is for easier 225-275 meter holds.

77gr 5.56 @ 2700 fps, standard 0ft atmosphere, drop in inches:

100 meter zero;
200 meters: -4.3
225 meters: -6.7
250 meters: -9.5
275 meters: -13.1
300 meters: -17.2

200 meter zero:
200 meters: -0.0
225 meters: -1.8
250 meters: -4.2
275 meters: -7.2
300 meters: -10.8

Basically this says that a 200 meter zero gives you an additional 50 yards of point and click over a 100 meter zero on a not overly generous target, and will need to accurately account for drop starting around 275 meters rather than 225.

Here's some stuff about the advantages of a 100 meter zero:
https://www.m4carbine.net/showthread.php?107572-Zen-of-the-100-Meter-Zero
For your particular application I would direct you toward the close range stuff.

So...
Why use a weird zeroing scheme to give a solution that is already given to you in a better visual format with a better baseline zero?