Bigjohn

05-09-2009, 03:20 AM

In the sport/hobby that we take part in B.C. (Ballistic Coefficient) is an important number to have.

So, here comes a question I have and so would many other shooters about what to do if that number is not available. How do we calculate what the Ballistic Coefficient of a boolit we have just cast is, if the mould maker has not provided it?

Also, how much would the change of metal mix/weight affect this number?

I have seen articles on various methods; one involving the use of two chronographs; one for the muzzle vel. and one to collect the velocity remaining at approximately 100yds and these figures are used to calculate the B.C..

As I understand it, this number is what we use to compare our boolits performance (trajectory, wind drift, fpe etc) at "whatever" velocity we are able to launch them from the firearm against a known graph.

There is still the old tried and true method of shooting the firearm and adjusting the sights accordingly but that all changes if you alter one or more of the perfromance parameters.

Please note; I'm terrible a maths, which is way I'm possibly asking this question. I just hope to learn more.

John

So, here comes a question I have and so would many other shooters about what to do if that number is not available. How do we calculate what the Ballistic Coefficient of a boolit we have just cast is, if the mould maker has not provided it?

Also, how much would the change of metal mix/weight affect this number?

I have seen articles on various methods; one involving the use of two chronographs; one for the muzzle vel. and one to collect the velocity remaining at approximately 100yds and these figures are used to calculate the B.C..

As I understand it, this number is what we use to compare our boolits performance (trajectory, wind drift, fpe etc) at "whatever" velocity we are able to launch them from the firearm against a known graph.

There is still the old tried and true method of shooting the firearm and adjusting the sights accordingly but that all changes if you alter one or more of the perfromance parameters.

Please note; I'm terrible a maths, which is way I'm possibly asking this question. I just hope to learn more.

John