Lapua B.C Question

[IceSniper]

I'm trying to make a drop chart for the .30cal 155gr Lapua Scenar using a new ballistics program. With this program, instead of just typing in the published BC like my old program i need the velocity that the BC is related to...

So is the BC that Lapua published (0.508) the BC for 0fps or say 2700fps? /ubbthreads/images/graemlins/confused.gif

 

[Mikecr]

I'd ask Lapua. You would also need to know the air density conditions for their BC basis.
But ultimately, you'll have to validate BC through shooting at your max ranges.

 

[IceSniper]

Thanks for the reply, Mike. e-mail to lapua sent

I've shot them out to 650y to try and work out my MV from the drop but thats a pain in the *** when you don't know the exact BC.

 

[Ridge Runner]

most ballistic programs will figure actual BC from the velocity and trajectory, does this work?
JS

 

[IceSniper]

James,
It would, but i'd need velocity figgers for the muzzle and 200y and i don't have a chrony.

 

[Desert Fox]

So far the factory published B.C for these bullets works for my rifle out to 500 meter. I'm using Exbal to calculate my drop at 500 meter. With my rifle zeroed at 100 meter The Exbal suggest 8.75 MOA at 500. The velocity of the load was 2845 fps, altitude at 2700 ft, 70 degrees ambient temperature and 60% RH. I'll be testing these bullet to 1000 meter when I'll get a chance. I'll post the result.