Let's start with a some facts.
1. Nothing beats confirmed data! (D.O.P.E book)
Your D.O.P.E book should be the best place to find data for your firearm. A ballistic calculator should not be a replacement for a D.O.P.E book.
2. A ballistic calculator is only as good as the information put into it. As the saying goes; garbage in, garbage out.
3. A ballistic calculator will not be perfect. (Sort of)
Because there are multiple things that affect multiple other things, when it comes to longrange shooting, the ballistic calculator's output will not match up perfectly to actual impacts. A head wind or tail wind will have an effect on the bullet. This will aid or hinder the bullet's velocity.
The barrel's twist rate will affect the bullet's ballistic coefficient, as well as any yaw the bullet may have. Bullet speed and gyroscopic stability will also affect a bullet's ballistic coefficient.
If all that wasn't enough to be overwhelmed with, there's more. If you look up a specific bullet's ballistic coefficient (depending where you look), you will see different G7 B.C. numbers. This is because some bullet manufacturers will stamp the box with the bullet's B.C. at the muzzle to get a higher number. Independent bullet tests will get the B.C. just before the transsonic zone. A bullet's B.C. will change during flight. You can also use multiple BC inputs to get a more accurate picture of a bullet's flight path. But again, there are other things that will affect a bullet's B.C.
With all the thing that affect a bullet and it's B.C, what do we do? It seems the best thing we can do is true the bullet's muzzle velocity and B.C.
Start with finding the bullet's correct B.C. for the distance you will be shooting. For me, this will be the bullet's "maximum effective range" (1300 fps or ,according to Brian Litz of Applied Ballistics, 1350 fps). This will be just before the bullet goes transsonic. Applied Ballistics uses this to publish B.C.s and, in my experience is the best way to go if using B.C.s to determine bullet drop.
Ex. Hornadys .264 (6.5) ELD-M 147 has a published G7 B.C. of .351, G1 B.C. of .697. This may be true at 200 yards, but at 1400 yards, this is not the case. It's closer to G7 B.C .315, G1 B.C. 622 (per Applied Ballistics). And when I use this as my B.C. input, then true my muzzle velocity, I am getting first round hits (almost center) at longrange and extreme ranges.
Now that I have the correct B.C., it's time to send lead down range to true my muzzle velocity. My ballistic calculator says my bullet will be 1300 fps at 1050 yards. So I'll shoot 5 rounds at 1100 yards because I don't have a target at 1050. The center of the group should be adjusted on the scope turret to be center of the target. I'll shoot 5 more to confirm. This is a good time to input this into your D.O.P.E book. At 1100 yards, I need 11.1 mils of adjustment to hit dead center. Now it's time to true my muzzle velocity.
Truing the muzzle velocity essentially fixes the small errors in the system (like a changing B.C.) to match the bullet's true flight path. This is done by going to the muzzle velocity correction/truing input in the ballistic calculator. Every ballistic calculator should have this option. In strelok pro and my Kestrel, I'll adjust the distance to 1100 yards and input 11.1 mils for my dope. I'll hit confirm and now my Kestrel and strelok pro app are trued. My tested muzzle velocity was 2686, and my trued velocity is 2656. Next, I'll confirm my Kestrel is correct from 200 - 1400 yards and input all the data into my D.O.P.E book.
Now that I have my data confirmed, I like to run some drills. One bullet per target, as far as I can shoot, as fast as I can shoot until I miss. I have video posted on my YouTube page truing and confirming my D.O.P.E at
https://m.youtube.com/channel/UCiGCc1ZHd93VmN4kZPvHscg
This has been by far the most successful way to get first round hits at extreme long ranges. Before I learned about truing, I wasted so much ammo walking bullets into the target because the information (per the bullet manufacturer) was incorrect.
The Overwatch
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