Need help with BC

Gambler

Member
Feb 20, 2023
266
105
Åmot
I started to use the zan 26.5 MK2 slugs in .25cal.
On his website he say they have a BC of .088.
I but my info in my BC app and in my alpex 4k, the app show a drop of 106cm at 155m and the alpex say 102.5cm
This is at 985fps avg.
I use scope hight 75mm on my M3 (if that has something to do with it)
When I shoot at my target at 155m i hit around 25cm higher than the alpex calculates (and the app since thay are just a few cm apart)
I tried to up the BC until i was around 85cm drop, but even i understand that theese slugs dont have over .160 BC.
Atleast i hit where I want now, but where is the actual error in my setup?
 
Oh, I see now that you're talking about a 3.8cm elevation drop difference at 155m in your calculation. Meh, that's a micro-variation that could be anything from environmental factors (wind, air density, humidity) to decimal scale BC differences of your bore specs. You could setup a second chrono near 155mm to calculate BC at that range.