Paging Sirgilligan (or anyone else ballistics savy)

[GTS197]

I need to zero my AACOG, which has the reticle's BDC set for meters; 100-800. The problem is, the range I shoot at is only set up for 100 yards.

Where will I need my POI to be at 100 yards, to achieve a 100 meter zero?

Ammo to be used is 55gr, .223/5.56 at approx 2950-3000 fps.

Nikon's ballistics program indicated hitting .03" low at 100 yds, but that was with a velocity of 3270 fps and the sight line being 2.5" above the bore line (which I believe it already is). If this is accurate, there really isn't much difference between yards and meters, with a 100 yard zero...approx .1" low at 400 yards, .2" low at 800 yards, etc...(theoretically, of course.)

[15ICAM]

Its an 8 1/2 yard difference which will be pretty negligible. You'd be a few thousands of an inch low at 100yds to get a 100m zero but in order to realize this, you'd need a 1/4 MOA gun or better.

Also in all likelyhood, the BDC in the ACOG was set-up for a weapon/ammo combo that you are not using so the BDC is only going to be a swag (close enough to hit a human at further ranges)

So after all that if you zero at 100yds, you will be close enough at all the other ranges.

An alternative is to zero the top of the verticle BDC line (the 300m reference) at 27.5 Yards (25m) to establish the 25/300 zero the Army loves so much and then confirm the 100m aimpoint is close at 100yards

[sirgilligan]

Sight Height 3.5"
MV 2950
BC 0.241
100m - 109 yard zero

100 yards = -0.1" (1/10" low at 100, this value could be -0.05 to -0.14 since the value is rounded to the nearest tenth for display)

25 yards -2.3"
30 yards -2.0"
50 yards -1.2"
55 yards -1.0"
75 yards -0.75"

[sirgilligan]

Sight Height at 2.5" (not the standard height for SCAR iron sights)
MV 2950
BC 0.241
100m - 109 yard zero

From 90 yards to 111 yards you are less than 1/10" from zero.

Yes, sight height makes that much difference.

with a 100 yard zero...approx .1" low at 400 yards, .2" low at 800 yards, etc...(theoretically, of course.)

Hmm, I don't think so.
400 yards -26.7"
500 yards -66.6"
600 yards -155.6"
800 yards -309.1"

A 300m zero with your sights at 2.5" would give:
100 yards 5.3"
200 yards 7.7"
300 yards 3.0"
328 yards 0.0"
400 yards -11.7"
500 yards -61.4"
600 yards -88.2"
800 yards -267.0"

You need lower sights, more velocity, and better ballistic coefficient to get .2" low at 800 yards. I don't know what gun can do that!

with a 100 yard zero...approx .1" low at 400 yards, .2" low at 800 yards, etc...(theoretically, of course.)

Wait, I get what you are saying... in your BC reticle you will be off a bit.Yes, I see now.

[GTS197]

Thank you!

I doubt I'll have to push the round out any farther than 400 yds, so the minimal variance is negligible. 15ICAM is correct, it's mounted on an AR, not a sub-MOA bolt gun.

[GTS197]

And of course...Gun Log isn't available for Android

[sirgilligan]

You guys and your Android phones...

Just kidding. I do this by myself and originally for myself. Coding to the Android device is easy, nothing stopping me but time to do it. The maintenance of two different code bases (JAVA and Objective C) can burn up the time. I want to get you all an Android version and I want to have a life too!

Maybe I will make a simple version with ballistic table, guns, ammo, and sessions. No reports, no photos. I don't know!

[GTS197]

Wait, I get what you are saying... in your BC reticle you will be off a bit.Yes, I see now.

Yes, I was referring solely to the differences while utilizing the BDC.

It's ok...us Android users will have to revert to some sub-standard ballistics program

[eddie gunks]

well,

i am trying to use this app on my i phone. it will not keep my weapon configuration so i can not get the bullet drop tables to work. what am i doing wrong?

eddie

[sirgilligan]

PM sent.