Range Report My Ballistic coefficient changes ALOT after 1200m

Ker

Private
Minuteman
Apr 13, 2013
2
0
I can get my clicks to match up to around 1200m. But from there and to 1600m my Ballistic coefficient calculator is way off.

I guess it have something to do with the bullet flight speed getting to low and the bullet drops even more.. or?


Rifle: Sako TTG-42
1 twist in 12in
Ammo: Lapua .338 250grains (16.20g)
Muzzlevelocity: 888m/s (2913 FPS) at 26C (78.8F), 913Hpa (26.93InHg)
Scopehight: 5.6cm (2.2in)
One click is: 0.100 (MIL)
Zero range 100m (109.4 yards)

Im using Bulletflight.

At 1600m im using 200 klicks.

So.. Need help figuring out WHY the Bc7 only match to 1200m and HOW i can calculate/get an accurate number from 1200-1600m. (besides shooting dope test)
 

damoncali

Gunny Sergeant
Full Member
Minuteman
Mar 19, 2011
1,376
86
49
Omaha, Nebraska
bisonballistics.com
As you approach mach 1, even a G7 drag function may be way off the actual drag. To work in that range, you need to somehow compensate for that. Bryan Litz's new program apparently has custom drag functions (I assume they are calculated, but that's way better than nothing) for the bullets in his library. I haven't used it and don't shoot that far anyhow, but I think this is your problem.