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Advanced Marksmanship How to convert inche drop at 1000 Yards to Mils
- Thread starter GBMaryland
- Start date
The "real math" isn't hard but its cumbersome to spit out in one sentence.
Quick 2-step overview:
step 1 trig for any 3 sides of a triangle = 3 known sides
step 2 more trig to get three angles (from 3 known sides)
More specifically, step 2 unfolds as follows ...
2.1 Trig function (cosine) using ratios of sides (soh-cah-toa) from 1.
2.2 Inverse-trig function (arc-cosine) to get angles in radians from 2.1.
2.3 Mil-radians conversion from 2.2
Quick 2-step overview:
step 1 trig for any 3 sides of a triangle = 3 known sides
step 2 more trig to get three angles (from 3 known sides)
More specifically, step 2 unfolds as follows ...
2.1 Trig function (cosine) using ratios of sides (soh-cah-toa) from 1.
2.2 Inverse-trig function (arc-cosine) to get angles in radians from 2.1.
2.3 Mil-radians conversion from 2.2
For some reason it's always been easier to remember by splitting it up into two thought processes for me...
I always remember the 1.047 and 3.6 numbers
Take which ever I'm using, and look at distance first.
Unit of measure x number of hundred yards gives me how many inches at that distance
3.6x10=36
Then take the inches and divide by that number
228/36=6.33333
For some reason that keeps it straight in my head and can be easier done off the cuff
Hope you've been doing well
I always remember the 1.047 and 3.6 numbers
Take which ever I'm using, and look at distance first.
Unit of measure x number of hundred yards gives me how many inches at that distance
3.6x10=36
Then take the inches and divide by that number
228/36=6.33333
For some reason that keeps it straight in my head and can be easier done off the cuff
Hope you've been doing well
Did you make the shot? I assume so since you were looking for MILs and didn't trust 22.8 MOA
. I hate how easy it is to convert inches to MOA but the cool kids use MIL so I guess I will
Wouldn't it be 21.8 moa ....Did you make the shot? I assume so since you were looking for MILs and didn't trust 22.8 MOA
It's a >10" difference being off a full minute, and enough to miss depending on the target
In my head I just use 1" per 100y but it's probably slightly more than that. If I was wrong, thanks you convinced me to never shoot MOA again because I couldn't get a simple 1000y conversion done in my head!!!
Yea "shooters" moa or inches per hundred is a common short hand.
About like using 3.5" instead of 3.6 for MIL conversion
Not trying to talk you our of anything, but if you are trying to convert numbers to true all your data then the 1 vs 1.047 or 3.6 vs 3.5 start to matter depending on how close you are trying to get your data
if you need operational 'redundancy', just carry spare battery/kestrel/iphone etc.
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.... can't decide if you think I'm trying to sell you on mils .... or trying to goat me into screwing with you about it .... hard to read inflection on the internet....
Anyway there is always error to be had in the rounding it's just how much everyone is comfortable with
I've chosen to shoot MILs even though MOA kinda makes more sense to me on the fly for estimation (but, as you pointed out even those estimates can be off by a bit at extended ranges). I went with MILs because it seems to be common among the guys I've learned from and I do like dialing in 0.1's instead of 0.25's.
All kidding aside, I really do appreciate you checking me on that because I've not run the number to see how much that rounding is off at 1k. And I'm just coping with having all MIL optics when MOA makes more sense to me intuitively haha
Yea about the same for me
Everything started in smoa
I was familiar with inches so it was easier
Now I just use the reticle and don't care as much
Now the .1 mil per mph wind bracket and dope plus a tenth per ten yards are like standard short cuts in my head... so everything is mils now...
I just memorized 1.047 / 3.6 and 3.438 / 3.44 if I need to convert for some reason all those are small enough numbers I can pencil it if need be
And I understand being confused...
Hell I now have 1/4 mil reticles ...
Dafuq
A simple rule that can help...
One mil is exactly 1/1000 of the distance to the target.
If you are shooting at 1000 yards, then 1 mil = 1 yard
If you are shooting at 1000 meters, then 1 mil = 1 meter
If you are shooting at a distance of 100 yards, then 1 mil = 1/1000 of 100 yards aka 1/10 of a yard aka 3.6 inches.
One mil is exactly 1/1000 of the distance to the target.
If you are shooting at 1000 yards, then 1 mil = 1 yard
If you are shooting at 1000 meters, then 1 mil = 1 meter
If you are shooting at a distance of 100 yards, then 1 mil = 1/1000 of 100 yards aka 1/10 of a yard aka 3.6 inches.
Get a databook as a backup. Have dope cards. People were doing this long before any of these electrical devices ever existed.EMP?
I, too, was an MOA diehard for the longest time.
Then I took a precision rifle course from Frank and Marc last summer and the light went on.
So for long range precision anything over 500 yds or so, I shoot MIL, for short range, general purpose shooting, MOA works just fine.
Remember, if you are using MOA @ 1"/100 yds vs 1.047"/100 yds, at 1000 yds and a 20MOA drop, you will be off by 9.4".
Just something to consider.
And don't even get me started about doping for wind.
Based off your bullet BC, which determines your "gun number", .1 mil/100 yds per wind mph is so much easier and intuitive.
For example, with a bullet BC of 650, that gives you a "gun number" of 6. So at a 6mph wind, you have a .1 mil offset every 100 yds. For a 12 mph wind, you have a .2mil offset for every 100 yds.
There is more to it than that, but basically, that's wind calling based on "gun number" and mils.
And don't forget ranging.
Using "gravity ballistics" you can dope your rifle out to 1000yds easily using mils.
Sorry for the long post.
Frank and Marc made a very strong impression on me in that course and I am a much better shooter because of it.
Then I took a precision rifle course from Frank and Marc last summer and the light went on.
So for long range precision anything over 500 yds or so, I shoot MIL, for short range, general purpose shooting, MOA works just fine.
Remember, if you are using MOA @ 1"/100 yds vs 1.047"/100 yds, at 1000 yds and a 20MOA drop, you will be off by 9.4".
Just something to consider.
And don't even get me started about doping for wind.
Based off your bullet BC, which determines your "gun number", .1 mil/100 yds per wind mph is so much easier and intuitive.
For example, with a bullet BC of 650, that gives you a "gun number" of 6. So at a 6mph wind, you have a .1 mil offset every 100 yds. For a 12 mph wind, you have a .2mil offset for every 100 yds.
There is more to it than that, but basically, that's wind calling based on "gun number" and mils.
And don't forget ranging.
Using "gravity ballistics" you can dope your rifle out to 1000yds easily using mils.
Sorry for the long post.
Frank and Marc made a very strong impression on me in that course and I am a much better shooter because of it.
Post #2 and #3 have the answer as generally known.
But for fun, here is this.
θ=s/r
where θ is the angle in radians, s is the intercepted arc, and r is the radius of the circle.
s=228”
r=1000yds=36,000”
So
θ=228/36,000
θ=0.00633333333….. radians
Multiply by 1,000 to convert to milliradians
6.3 milliradians
