Range Report I don't get it! Mil vs CM in Sierra v6

[st1650]

So I have a Falcon 4.4-14 FFP mounted on a AR10T. Reticle is ML16 ( http://www.falconoptics.com/pdf/FFPML16Master.pdf ) and turrets are in Mrad (1 click = .1mrad or 1 cm @ 100 meters)

So let's say I zero it at 50 meters using AMAX 168gr 2600FPS. 2.2" sight height.

Sierra gives me 3.5 mil in drop for 500 meters which mean 35 clicks on the turret.

But, if I calculate the drop in centimeters, Sierra gives me 190.88 cm of drop which means 38.18 cm @100meters which means 38 clicks. Where the hell does the 3click difference comes from ?

I've googled and looked on the wiki and it does say 1rad= 1meter @ 1000 meters.

 

[ChadTRG42]

Re: I don't get it! Mil vs CM in Sierra v6

Here's the drop I come up with. I get a difference of .23 mils from a 50 to 100 yard zero. I would zero at 100 and not 50. Don't worry about the centimeters, just work in mils. I don't get the 190 cm, so I don't know about that. I get 157 cm and 147 cm, depending on which zero.

Zero at 50
Range Elev Wind
(yards) (mil) (mil)
0 --- ---
50 0 0.11
100 0.23 0.22
150 0.03 0.33
200 -0.3 0.45
250 -0.7 0.57
300 -1.13 0.69
350 -1.61 0.82
400 -2.12 0.96
450 -2.67 1.1
500 -3.26 1.25

Zero at 100
Range Elev Wind
(yards) (mil) (mil)
0 --- ---
50 -0.23 0.11
100 0 0.22
150 -0.2 0.33
200 -0.53 0.45
250 -0.93 0.57
300 -1.36 0.69
350 -1.84 0.82
400 -2.35 0.96
450 -2.9 0.96
500 -3.49 0.96

 

[CarolinaExPat1]

Re: I don't get it! Mil vs CM in Sierra v6

Eric,

The difference can come from a number of things. I've used the Horus vision software and found differences from actual range results so the first possibility could be an incorrectness of the software. While the math plugged into the formula will give you either 175cm's or 190.88cm's, both of those are estimates of the actual drop. The next possibility could be the variable of zero range. I'm not trying to insinuate that you input your data wrong, but if you did, the results would change from a short range trajectory standpoint to a long range trajectory standpoint. When we go downrange we realize that all our shit is an estimate. Unless we're using a laser rangefinder we have to go off of Mils, so we'd take my shooter's results and my results and average them out. For your drop that might be a possibility if you needed first round hits. If your application is for range purposes only, average them out and then work off of your target feedback. Record it all down in your databook and you'll know "ok, I really need 36 clicks." Just an example. Also, your AMAX bullets may have flatter trajectory than M118LR even with similar ballistic coefficients. That may be where the difference is coming from. One last suggestion is to zero at 100meters with a .308. 50 will give you dramatically different results in your elevation changes due to the sight angle to target. 100 is where you need to be. Hope that helped but ultimately you'll just need to trial-error it all.

 

[st1650]

Re: I don't get it! Mil vs CM in Sierra v6

This is driving me nuts! I know it's only theoretical values. I'm not working with field values, only theoretical. Sierra seems to adjust with a 1.09x factor everywhere except in their Tactical/Mil calculation. It does the same thing both in yards and meters.

Ex. Again same values : 168amax, 2600FPS, 21C. 50 yards zero. 2.2" sight height.

Drop from sierra 6: 57.23 inches at 500 yrds
Drop from sierra v5.1: 57.1 inches at 500 yrds
Drop from Prof. Arthur J Pejsa formula : 62.16
62.16/57.23= 1.09

Same 1.09 as 38.18/35!
Where the hell comes the 1.09. And it's not because I mix yards and meters!


I know it's different in the field but I just can't get over such an error margin in theory.

 

[Rob01]

Re: I don't get it! Mil vs CM in Sierra v6

Run your data in mils and stop thinking in clicks. You need 3.5 mils you dial to the big 3 on the dial and then to .5. Simple. No counting clicks.