B.C. Variance

Hunter

Well-Known Member
Joined
Jan 18, 2002
Messages
69
Location
Alaska
Could someone tell me what the best way is of allowing for the change in ballistic coefficients at the various velocities over long range for use in computer trajectory calculations?

For example, a given bullet has BC is .450 at 3100fps, .440 at 2400fps, and .372 at 1600fps. What BC value would one use for an accurate trajectory calculation for the entire range of velocities?

Do any of the software programs that are available allow for changing BC values or do they all make the calculations with just one value?

TIA
 

RBrowning

Well-Known Member
Joined
Feb 8, 2002
Messages
247
Location
Jackson MI
The Sierra Infinity program allows you to enter up to 5 different BC values and the velosity threshold for custom bullets that you set-up in the program. It will also allow you to put in a max range of 8000 yds. That seems a bit long even for the folks around here
 

Hunter

Well-Known Member
Joined
Jan 18, 2002
Messages
69
Location
Alaska
RBrowning, thanks. I just got an email from Robert Treece at Sierra and he confirmed what you said. I have a copy of Infinity ordered.
 

Brent

Well-Known Member
Joined
Jun 12, 2001
Messages
2,537
Location
Palmer, Alaska
RB,
Do you mean five different drag curves like the Oehler Ballistic Explorer program does, which has 7, one of which is for rimfire, or is this something else completely?
 

RBrowning

Well-Known Member
Joined
Feb 8, 2002
Messages
247
Location
Jackson MI
I'm not familiar with the Oheler program so you will have to draw your own comparisons. The Serria Infinity program allows you to define a bullet if there isn't one already in their library. You can put on diameter, weight etc., then you can put in up to 5 BC values and the threshold values for velocity where the BC will change. Generally the lower the velocity the lower the BC. My guess by looking at the values that they post for their own bullets is that you would get a curve if they were plotted. I don't shoot exotic bullets (LRB etc) so I just use what is in the library.

If you do get the software make sure you go to their site and down load the update. It takes a while to download 2.3M but it is worth it - more in the library, more features and runs faster.
 

Trending threads

Nightforce has great tracking capabilities, they are rugged, a bunch of elevation, holds zero forever, and reticles are designed for long range shooting. So if you are looking to shoot long distances constantly, then you need a scope that can take the abuse. -- gilmillan1


Culture Of Excellence At Nightforce Optics
By Len Backus

A high level of quality both in production and in service. Read More


Nightforce is such a solid combo of reticle, available elevation, glass that is good enough to shoot at the longest range you can dial. Nightforce has bullet proof construction that can handle the incidental horse rolling or some other rodeo action. -- bigngreen


Nightforce ATACR Scope Review
By Jeff Brozovich

The new NightForce ATACR is for sure a top choice for any long range shooter. Read More


The total package. Nightforce is the best I have used as far as turret feel and solid detents. I have never had one that didn't track right on and always return to zero. Nightforce NXS is the best value for everything I need. -- Broz


Nightforce Velocity 1000 Reticle Review
By Scott Shreve

I think Nightforce knocked it outta the park with this reticle! Read More

NightForce


Top