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View Full Version : Ballistics Question (Calibrating Matech Yards vs. Meters)


GettoPhilosopher
12-11-2011, 12:11 AM
Alright, I'm still learning how to do ballistics calculations and the like, maybe some of you veterans can help me.

I've got a 20" M16A4 clone with flat top upper, Matech 600m sight, and normal FSB. I like it. I really like it. I want to be able to use the adjustments on the sight.

Unfortunately, all the ranges I shoot at are in yards. I'm playing with ballistics calculators trying to figure out the offset between yards and meters shooting M193 (55gr FMJBT .223 rounds).

In other words, I want to know how to zero it at 25y (I think I figured this one out....POI = POA + 0.2"), and I want to know how the meter calibrations will match up to yards. I.e. the 200m setting will be X.X inches high/low at 100 y, X.X inches high/low at 200y, then the 300m setting will be.....etc.

Essentially, I want to print up a range card for my sight (and later for my ACOG) that'd make it easy. Say like this:

RANGE: 100Y SIGHT SETTING: 200M OFFSET: +2"
RANGE: 200Y SIGHT SETTING: 200M OFFSET: -0.5"

Or whatever the numbers actually come out to.

I know SOMEONE has to have figured this out already, if only because ACOGs are calibrated for meters as well. I'm searching and not finding anything, but I'm sure someone has calculated out the bullet drop and plotted it out.

GettoPhilosopher
12-11-2011, 12:12 AM
Ok, I've got a rough way of doing it. I'm running a different JBM calculation with a different zero distance per setting on the sight. So zeroed at 25m, I can look and see that at 25y, I will be .2" low, at 50y I will be 2" high, and at 100y I will be 5" high....etc.

Now I realize the second problem: The sight is calibrated for M855, which has a different trajectory profile than M193. How badly is this going to screw up my calculations? The problem is, I know don't how to calculate the actual adjustment amount of the sight between the different distances, so i'm forced to solve by ballistic calculation. If POA = POI on the 25/350m setting at 25m, then POI is 2" high at 50y, etc. But since those calibrations only work perfectly with M855, I have to figure out how much I'll be off using 55gr M193.

Help?

killshot44
12-11-2011, 11:42 AM
Te programs will get you close.
Better to actually shoot the distances desired and mark your rear sight accordingly.
It is what most Service Rifle competitors do.

GettoPhilosopher
12-11-2011, 1:04 PM
Sight Setting Known Distance to Target POI
25/350m 25 y -0.2” (Zero it .2" low at 25y)
200m 25 y -1.3
200m 50 y -0.2
200m 100 y 1.2
200m 150 y 1.6
200m 200 y 1.3
200m 250 y -1.6
300m 300 y 2.3
300m 350 y -2.3
25/350m 400 y -1.7
400m 450 y -2.3
500m 500 y 11.3
500m 550 y -0.8
600m 600 y 21.2
600m 650 y 2.6


That's roughly what I got. It's going to get less accurate the further out I get due to the difference in calibration between M193 and M855. There's not really any good option for 500y and 600y, both are crap choices between way too low and way too high, but hey....it's a BUIS.

GettoPhilosopher
12-11-2011, 5:42 PM
Worked well enough for me on the steel at Angeles at 25/100/200/300/500y. :)

Sent from my Galaxy S II. Please overlook any typos.

30Cal
12-11-2011, 7:04 PM
For shooting purposes, yards is the same as meters out to about 500yds.