How can I determine my actual BC?

[sewwhat89]

I am not getting anywhere close to the ballistic tables some of you guys are listing with published bc values at STP. How can I go about calculating my own bc? I know the ballistics for my 300 SAUM shooting 178 gr AMAX (.495 bc)and 175 gr SMK (.505 bc). The AMAX shoots flatter at 500m by about 4 inches. The muzzle velocities are the exact same. Is the AMAX bc low or the SMK high? Thanks!

With 100 yd zero:

175 gr SMK 43 clicks to 535 yd zero
178 gr AMAX 40 clicks to 535 yd zero

 

[Charles A]

The 178gr Amax is really more like .525bc

 

[sewwhat89]

Good, I played with the numbers and that is what I determined it to be based on the ballistics program and its parameters. Thanks!

 

[davewilson]

is this like a 3 part equation where if you have 2 known's you can figure the third or does temp, humidity, and the lunar equinox come into play. for basic purposes,if you have the muzzle velocity and either the drop or velocity at a certain range,the farther the better i presume,then the B.C. can be obtained? does anyone have a formula where the numbers can be plugged into.one thing is for sure,when i get a really good B.C.,i'm gonna post it on here.it's been a little slow lately!

 

[Charles A]

Dave, kind of. If you know the velocity, and measure the drop, you can get the B.C. for that bullet in your rifle, though it wont be exactly accurate if you dont put in Enviromental conditions. Put in bullet weight, velocity, height above bore, temp, BP, and play with it untill it matches your measured drop. Or you could just come here and ask what the real BC is. /ubbthreads/images/graemlins/grin.gif

 

[sewwhat89]

What do you have as the bc for the 175 gr SMK?

 

[Charles A]

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What do you have as the bc for the 175 gr SMK?

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.505