Could someone give a step-by-step example of this? If POI is, say, 4 inches high at 1000, does this mean the MV is higher than you thought? And then, is the BC adjusted up or down, and by how much? Never used this approach. Thx.
Truing with BC
- Thread starter Dunraven
- Start date
Depends on a few things.
Are you using g7 or a custom curve? If a custom curve, you will only be able to mess with the MV.
Typically, past 600yds or so, it’s going to be the BC. So, your BC is slightly higher than what you have in your calculator.
Also, keep in mind, 4” at 1k is less than .5moa. Make sure the center of your group is actually high, as you could easily be inside the capability of the rifle and/or shooter.
If it were me, I would true data at 3, 6, 8, 1k yds.
I would then tweak the B.C. so the 800 and 1k lined up. I’d then check to see if the 3 and 6 lined up. If not, I’d tweak MV to make those line up.
For 1k, record what it took to get on water line.
Say it took 6.2 instead of 6.6mil.
Your B.C. is calling for .279. Change it to .280 or .281, etc etc. until it matches the 6.2 in the calculator.
Make sure the rest of your verified dope still lines up with the calculator.
Sometimes it will and you’re g2g. Sometimes your <600 yd dope is a little off and you need to tweak MV.
You can also use the MV calculator in the kestrel and use the velocity it gives you. If all your dope lines up, that is ok as well.
Lots of ways to skin this cat.
Don't tweak it. How sure are you of your muzzle velocity, what did you measure it with? Have you verified your scope tracks correctly? Have you noticed repeated hits on a water line that are low at 1k? Why do you think it's low?
Most of those are more likely issues than the BC being off by 4" at 1k.
Most of those are more likely issues than the BC being off by 4" at 1k.
You determine MV by chronograph, then true the BC past 600 yards.
What do you do when your dope doesn’t linenup inside 600yds?
I'm not having issues! I have been using ONLY MV to 'true' the kestrel readings. I just wanted to know how to do it using BC. I understand now that MV is used under 600, and BC beyond that. Wasn't sure the procedure on the kestrel for changing BC there.
The easiest way to true the BC is to start with the Middle Number
Tweak the Middle up or Down as necessary,
BCs are fluid, in other words they are dynamic and based on your MV and Rifle System as a whole.
So truing a BC should be as natural as truing the MV and in fact with Labradars and MagnetoSpeeds the first step when you consider their inherent accuracy over the old Sky Screen Models.
The BC number is an Average based on a short-range test using a specific system that is probably not what you are shooting
Tweak the Middle up or Down as necessary,
BCs are fluid, in other words they are dynamic and based on your MV and Rifle System as a whole.
So truing a BC should be as natural as truing the MV and in fact with Labradars and MagnetoSpeeds the first step when you consider their inherent accuracy over the old Sky Screen Models.
The BC number is an Average based on a short-range test using a specific system that is probably not what you are shooting
My point was, before you fuck with the BC to get the prediction of the Kestrel to match what you see in real life, have you verified there's no issue with more likely sources of error in your ballistic solution.
If you're 4" high at 1k, I'm saying it's more likely your scope isn't tracking or maybe your MV is wrong, hell your zero might be off. If you're sure all that is good to go, THEN screw with BC a bit.
If you're 4" high at 1k, I'm saying it's more likely your scope isn't tracking or maybe your MV is wrong, hell your zero might be off. If you're sure all that is good to go, THEN screw with BC a bit.
