About Ballistic Coefficient

[Koda]

I understand how and why advertised velocity can be different in my gun, and I have a chronograph to measure my actual velocity.

My guess is a bullets Ballistic Coefficient (BC) can also be different than the advertised BC. Is there a way to measure or determine the actual BC I am getting in my rifle?

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[Kruel J]

Shoot on a really windy day, into the wind?

 

[Kruel J]

If the shape and weight are accurate, the manufacturers stated BC should be good (temp, elevation, humidity and air pressure of course will vary).

 

[oremike]

https://winchester.com/Blog/2017/11/understanding-bullet-bc-ballistic-coefficient

 

[Kruel J]

Ballistic coefficient calculation NEW – Sellier & Bellot

www.sellier-bellot.cz

 

[Koda]

I understand how BC affects flight, windage, trajectory etc. Im curious if there is a way to measure the BC I'm actually getting in my rifle?

 

[Kruel J]

I understand how BC affects flight, windage, trajectory etc. Im curious if there is a way to measure the BC I'm actually getting in my rifle?

Not that I know of. And what would be the advantage? Assuming its not a manufacturer defect, the BC on the box should be enough. Besides the fact of some or even all the variables in my first post changing often from day to day or "trip to trip". Even if you know it, how would you convert it to "real world" usable information? The BC will even vary from round to round slightly needing manufactures to post the average.

 

[oremike]

I understand how BC affects flight, windage, trajectory etc. Im curious if there is a way to measure the BC I'm actually getting in my rifle?

Your rifle doesn't have anything to do with the BC, it's built into the bullet its self.

 

[Koda]

Not that I know of. And what would be the advantage? Assuming its not a manufacturer defect, the BC on the box should be enough. Besides the fact of some or even all the variables in my first post changing often from day to day or "trip to trip". Even if you know it, how would you convert it to "real world" usable information? The BC will even vary from round to round slightly needing manufactures to post the average.

The advantage is in long range shooting, all of the environmental elements can be calculated for in the field. If your BC is way off then that all goes out the window.


I do know that the advertized velocity can way way off from the actual velocity, so I suspect the same with the advertised BC. Im hoping your right its close enough.

 

[Koda]

Your rifle doesn't have anything to do with the BC, it's built into the bullet its self.

good point, but then is the advertised BC close enough?

 

[Kruel J]

@Koda what distance are you shooting at that you are questioning BC?

 

[RX-79G]

I understand how BC affects flight, windage, trajectory etc. Im curious if there is a way to measure the BC I'm actually getting in my rifle?

Fire through two chronographs - one at the muzzle and another 300 yards away.

 

[oremike]

good point, but then is the advertised BC close enough?

I think so, it's what we all use.

 

[Koda]

@Koda what distance are you shooting at that you are questioning BC?

im going for 500yds

 

[Koda]

Fire through two chronographs - one at the muzzle and another 300 yards away.

Can it be done only 100yds apart?

So you get two velocity numbers, and a distance spread, how do you use those to calculate actual BC?

 

[Kruel J]

im going for 500yds

That's a fairly "short" long distance shot. The box will serve you well.

 

[Koda]

That's a fairly "short" long distance shot. The box will serve you well.

if thats the case then I should be good estimating drops with a ballistic calculator. I'll start with that.

 

[RX-79G]

Can it be done only 100yds apart?

So you get two velocity numbers, and a distance spread, how do you use those to calculate actual BC?

Use a ballistic calculator and see if the velocity lost over the distance matches the BC input. If the loss is lower, your BC is higher than advertised.

 

[Koda]

Not that I know of. And what would be the advantage?

To add to this I want to order a custom turret dial and while I might not need to shoot past 500yds right now I want it to be accurate at any distance.

 

[Kruel J]

To add to this I want to order a custom turret dial and while I might not need to shoot past 500yds right now I want it to be accurate at any distance.

Custom turrets are great, absolutely.