Does my Bullet drop math make sense?

Tactical308

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THE FOLLOWING POST IS INCORRECT. I HAVE LEFT IT HERE JUST FOR REFERENCE TO THE LATER POST. CHEERS


Good day,

Being new to the long distance precision shooting world there are a million questions that run though my mind every time I think about this sport. I am sure there are more people out there thinking the exact same thing so maybe we can clarify some things.

I have been shooting at 100 yards (100 Yard Zero) for some time but I am starting to shoot further now. I think I understand the concept of Bullet drop vs. Clicks but I was hoping I could run it by you guys to see if my logic adds up.

First off I am running a Bushnell 3200 5x15 with target knobs on a Tikka T3. The scope is set at ¼ MOA increments.

So the way I see it, 1 MOA @ 100 yards equals 4 clicks. The target knobs have 12 MOA per rotation which works out to 48 clicks at 100 yards. The scope is said to have 50 MOA all together which should mean that I can do a total of 4 full rotations and 2MOA and no clicks (which I will refer to as 4R 2M 0C). Hopefully I am doing fine with my math so far.

So I am going to assume we are shooting a .308 match bullet (I am just going to make up drop values to make this easier) and that the bullet drop goes as follows:

Zero’d @ 100 yards
-0.5” @ 200 yards
-1.5”@ 300 yards
-3.5 @400 yards
-5.0” @ 500 yards
Blah Blah Blah
-25”@1000 yards

I realize these are probably really unrealistic but again it’s just to make the example easier to work with.

So let’s say I am sitting at the shooters bench now zero’d at 100 yards and I want to shoot at a target 300 yards away. I look up my bullet drop and notice that it drops -1.5”. So if it takes 4 clicks to move a bullet 1” @ 100 yards, now it will take 12 clicks (4clicks X 3 = 12) to move that same bullet over 1” at 300 yards. Since we are shooting at 300y and the drop is 1.5” we calculate to 18 clicks OR 4M 2C.

So let’s try a 500 yard shot. It would take 20 clicks to shift a bullet 1” at 500 yards. We notice that bullet drop for 500y is -5.0” so 20x5=100 clicks OR 2R 1M 0C.

Ok one last one.
Its time for the last shot. 1 Bullet left! But the target is 1000 yards away. So 40 clicks shifts a bullet 1” at 1000 yards. So 40x25=1000 clicks

48 clicks goes into 1000 clicks 20 times and your left with 40 clicks divided by 4 (amount of clicks) = 10. So you would have to Adjust 1000 clicks OR 20R 10M

Seeing as my scope only has 4R 2M 0C worth of adjustment I would not be able to make that shot without using a shim or re-zeroing at a longer distance to reduce the amount of bullet drop.

Does that make sense or is my math way off?

Cheers
 
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Your math IS wrong.

"So let’s try a 500 yard shot. It would take 20 clicks to shift a bullet 1” at 500 yards"

Negative - You're doing the math backwards! :)

One 1/4 MOA click would move the impact 1.25" at 500yards. MOA at 500yards is 5" (approx).
 
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You are a bit off my friend

These are the adjustments
1/4 MOA click on scope = about 1/4inch at 100 yards
1/4 MOA click on scope = about 1/2inch at 200 yards
1/4 MOA clcik on scope = about 3/4inch at 300 yards
1/4 MOA click on scope = about 1 inch at 400 yards
and so on
 
I would suggest forgetting about clicks, learn your comeups in minutes of angle for each range, then use the scale on your adjustment knob to set the elevation.
If you experiment with your scope you will notice that the clicks and the calibrations on the dial match, so you don't need to bother with the clicks. If you need a comeup of 16 minutes, it is a lot easier to wind this on using the graduations, than counting 64 clicks.
 
Look up JBM ballistics software on Google and you will get to the internet freeware. Great program and will let you play to your hearts delight. Most bullets are now in the database making calcs easy.

The data sheet that is generated will give you number of mins needed to reach your distant target. Those come ups are usually set with a 100yd zero but that can be modified to whatever you wish. It will also give you total amount of drop in, wind drift, lead, velocities, energies etc.

With your generated drop chart, a calibrated rangefinder, ammo and rifle, you start shooting at various distances. Let's say you range a target at 500yds. You look at your chart and it says 15mins of up from your established zero.

Dial up 1 rev and 3 mins, hold on target and fire. If you, the optics, and rifle are dialed in, you will get a hit. Don't bother counting clicks, it will drive you nuts.

ALWAYS return to your zero setting at the end of your shooting day. Better yet, before engaging your next target. It will only take you to forget once to understand my reasoning...

I have an article in my sig that might help you with your rifle set up. It is alot easier then you are making it. Simplify....

Jerry

PS your drop at 1000yds with the garden variety 308 is not going to be 25" but more like 29 FEET (approx 35mins or 350 inches).
 
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Not sure about your clicks and moa mumbo jumbo but, your drop tables are way off, bullet drops way more at all ranges. Eg. 200gr. spitzer at2300fps..100yd.zero.........200yds.-7.26"......300yds.-24.39"....400yds.-53.76"......500yds.--98.59"...600yds.-162.60"
 
Thanks for the advice.

You guys mentioned alot of good stuff and obviously iam doing things wrong. I dont want to just download a program that does all this for me. I want to understand how they get the numbers rather than just get a program to do the number crunching for me.

As for the bullet drop. As i mentioned I was just making up numbers just to make things easier.

Cheers
 
Take a look here http://www.handloads.com/calc/

Range Velocity Impact Drop ToF Energy Drift
0 2800 -1.5 0 0 1201 0
100 2497 5.12 2.62 0.12 955 1.53
200 2222 6.11 10.87 0.24 756 4.97
300 1964 0 26.22 0.39 591 11.18
400 1727 -15.19 50.65 0.55 457 20.67
500 1513 -42.13 86.83 0.74 351 34.04
600 1328 -84.34 138.28 0.95 270 51.87
700 1180 -146.29 209.47 1.19 213 74.5
800 1074 -233.09 305.5 1.46 177 101.73
900 999 -349.73 431.38 1.75 153 132.86
1000 944 -500.7 591.59 2.05 137 167.26
This may help you
Good Luck
 
Divide the drop by the distance to get the mumber of minutes required.

If the drop is 36 inches at 500 yards, divide 36 by 5 = 7 minutes. Come up 7 minutes.

Learn to read you turret markings. One it is zeroed, count the number of lines up from the bottom, say 3. If the turret is set to the number 6, your zero can be noted as 3-6. Note the same for each distance you shoot at and establish an elevation.

Just to make sure I know where my wind zero is, I not only note the sertting as descroibed, but i take a pencil and make a mark under the edge of the turret onto the turret barrel. Then I can confirm at a glance that the wind zero is where it should be.
 
Hey everyone,

Ok I reworked my numbers (obviously I was doing something wrong) but I think I have it now. I realize this looks like alot of information but its actually pretty simple. I just want to figure out a system of calculating so that I can understad the procedure. I can always simplify later.

So lets say I know my target is 500 yards away.

Section 2 has my bullet drop. So if I am zero'd at 100yards and shooting at 500 yards I can expect my bullet (see chart plz) to drop -64.6". I'll round to 65" for ease.

So if we look at page two we can see that I need to go 1 revolution of my turret plus 1 MOA up.

we'll skip the elevation/slope change section.

Section 4 is wind. So again iam gonna assume a 15MPH oblique wind from NE to SW at 500 yards gives me 25" drift. So again I look at page 2 and notice that I have to adjust 5MOA to the right.

Mind you all this information is based on a 1/4 MOA turret system with 12 MOA per revolution.

MOA1.jpg


MOA2.jpg


Hope my math is right this time.

Cheers
 
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