I have developed a new chart that will be taped to the side of my scope as a quick reference guide. Not only is it quick, but it’s very accurate as well. I did use my Kestrel with Applied Ballistics to confirm the data and it was spot on. There are a few things that can be modified to make if faster, but all in all, I’m very happy with it. It does have certain limitations for long range, but for real world applications and out to long range (about 800 yards), it’s awesome!!
My chart has my trued and verified dope out to 1000 yards, (This is very important to this chart or any Ballistic calculator), wind per 1 MPH, and cosine values for wind direction.
It also has my gun’s quick drop number, quick wind value, along with the yardage that the quick drop number is accurate between. Let’s take a look at it.
Fig 1
Fig. 1 is what is printed out and taped to my scope. It’s color coded to help keep track of what numbers relate to what yardage. An example of this is the green “QD 2.2” and green “300 - 770”. This lets me know if I use my QD number, it’s only accurate (within .2 MILS) between 300 - 770 yards. The Yellow QW 6.3 correlates with the yardage between 100 and 600 yards. This means with a 6.3 (I just call it 6) MPH wind, I will need to hold .2 Mils at 200, .3 Mils at 300, and so on up to 600 yards. I know at 700 - 800, I will need to add and additional .1 Mils, 900 and 1000 .2 Mils.
Let’s take a look at how easy this chart is to use.
Elevation
For elevation, I take 1/100 of my distance and subtract 2.2. The 2.2 is my Quick Drop (QD) number. 300 yards becomes 3.0, 450 becomes 4.5, 680 becomes 6.8. This will give me my elevation between 300 - 770 yards within of .2 mils.
Ex: 550 yards
5.5 - 2.2 = 3.3 Mils
630 yards
6.3 - 2.2 = 4.1 Mils
I can also reference the column on the far right to be more accurate. (.08 mils or less)
All I have to do is find the QD number for the yardage and subtract that QD number for 1/100 of my range.
Ex: 800 yards
8.0 - 1.9 = 6.1 Mils
760 yards
7.6 - 2 = 5.6 Mils
Wind
The chart gives me my wind at 1 MPH. With out using math it also gives me 10 mph wind by simply moving the decimal point to the right one time. So, .12 becomes 1.2. Because I included my quick wind number of 6, I will have 1, 6 and 10 MPH wind. With very simple math, it also gives me my 5, 15, and 20 MPH wind. If I need a 5 MPH wind hold, I simply move my decimal point over to the right once and divide by 2 or multiply by .5, depending how your brain works. At 500 yards, .08 becomes .8 (for 10 MPH) then cut that in half to .4. for a 15 MPH wind, simply add the half back to my 10 MPH wind hold. .08 becomes .8 divided by 2 = .4. .4 plus .8 = 1.2 Mils. For a 20 MPH wind, i just double my 10 mph wind. For any MPH wind, I just multiply my 1 MPH wind value by my wind speed.
This chart also has the correct cosine for the wind angle. Using the cosine will give me the most accurate wind hold. If I need speed over accuracy, I can round the cosine for 1:30 and 2:00 o’clock to .75 and 2:30 to 1. This gives me both options of speed and accuracy.
If I have a 5 MPH wind from 1:30 at 500 yards, I’d simply multiply 5 x .08 = .40. This I can do in my head very quickly. The next step is to divide by 4, to turn my whole number into 1/4. .40/4 = .1.
Then, I’ll use my rounded cosine of .75 (which is also 3/4. .1 x 3 = .3) as my wind hold.
Coriolis and Spindrift
I live in the northern hemisphere, so Coriolis will move my bullet to the right. Because I have a right hand twist barrel, spindrift will also move my bullet to the right. So, to adjust for Coriolis and spindrift, I will dial .1 Mil to the left.
Most of the math I can do in my head and have a firing solution within about 5 seconds. To get the best accuracy, I will use the cosine between 1:30 and 2:30, but I need a calculator.
Let’s run through a few scenarios:
EX. 1
Range - 650 Yards
Wind - 4 Mph @ 1 o’clock
Elevation
At 650 yards, my QD number is -2.2. 650 turns into 6.5
6.5 - 2.2 = 4.3 mils U
Wind
Because I am shooting half way between 600 (.1 Mil) and 700 (.12 Mil), I will use the number halfway between .1 and .12 which is .11 Mil
.11 x 4 (wind speed) = .44
.44/.50 (cosine) = .22 Mils R
Coriolis and Spindrift - .15 L
Elevation - 4.3 Mils
Wind - .07
For this example, I specifically picked a 4 Mph wind hold. With a 4 Mph wind, 1 Mph is my 1/4 wind. This removes some of the math, making it easier and faster. With an 8 Mph wind you can simply use 4 mph then double your answer for easy math.
EX. 2
Range - 800 yards
Wind - 10 Mph @ 1:30
Elevation
At 800 yards my QD number is -1.9
800 turns to 8.0 - 1.9 = 6.1 Mils
Wind
.14 x 10 = 1.4
1.4 x .707 = .98 Mils R
Coriolis and Spindrift - .2 Mils L
Elevation - 7 Mils
Wind - .78 Mils
Depending on the math, I can make the calculation by using the cosine .707 or 70%, and either calculate 70% of my wind (with a 10 mph wind 70% would be 7 mph) or calculate 70% of my wind hold. In this example, it’s easier for me to calculate 70% of a 10 mph wind (7 mph) and multiply that by my 1 MPH wind (.14)
.14 x 7 I can do in my head
1.4 x .70 I need a calculator
It just all depends on how you see numbers and what makes sense to you.
From the chart’s data and the examples, we see what the chart can do. Let’s talk about what it can’t do.
The most obvious is, that it is limited within a certain range. The good news is that the range is pretty far. 840 yards with my gun and ammo.
This chart also doesn't account for temperature variations. However, I can make an educated guess and still be within my error factor to hit vitals. I know if it’s cold, my ammo temperature will be lower, causing my bullet to have a lower velocity. This means I’ll impact low. So, for every 20 degrees, I can add or subtract .1 mil.
It also does not account for things like the elevation of a head or tail wind or vertical Coriolis. Again, I can make an educated adjustment. Between 700 and 840 yards, I can come up or down .1 Mil to adjust for a head or tail wind.
I Designed this chart to be accurate first, and quick second. Just like I went over above, the cosines can be rounded to make it much faster. Give it a try and see how you like it!
The Overwatch
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