Ballistics Program question?

[DB33]

I was wondering about drag function and or BC how to use them. I have been playing with the eskimo program trying to build a chart for my rifle that is a 300 win pushing a 168 berger vld at 3150 mv.zeroed at 300yrds The top of the berger box lists the bullet with a .512 bc I know that the true bc differs from rifle to rife but this is where I started using the g1 drag function and .512 bc I printed a chart using these and went to the range. Started at 8oo yrds and was consideralbly low so I started adding clicks approx 3 min, until I was hitting steel when I got home I played with the drag function but nothing seemed to fit the #s I had for 800 so I started reducing the BC until the #s fit,I am down to down to .450 bc still using the g1 drag function. Is this the right direction to make a good chart or am I missing something else? thanks DB

 

[Michael Eichele]

You are on the right track.

After shooting in the real world, take your data and make a ballistic program match by manipulating the drag function and BC. Note that most BC number's when used on a scale other than G1 are generally lower in number than the BC's that are based on G1. This doesnt meen that it is a bad thing. The high G1 BC's are more marketing hype than anything. Anyway, back to the program. Just make sure that you input accurate enviornmental factors such as temperature and the like. Also, if it takes 100 clicks on a .25 MOA scope this doesent meen that the bullet dropped 250 inches. Rather 100 clicks would equal 261.75" due to the differance between MOA and inches. A scope (provided it was made and distributed accurate) with .250 MOA/click is .26175" per click. From counting clicks, you can get a rough idea how many inches your bullet dropped from zero.

Regards!

 

[Michael Eichele]

I also meant to add to my first reply. When you are trying to come up with an accurate BC and drag model for your loads, it is ABSOLUTLEY critical to ensure you are inputing the correct atmospheric conditions. This will include Temperature, humidity, and barometric pressure. Altitude is meaningless unless you dont know the raw pressure, then use altitude and hope the pressure that day was average and not unusualy high or low. Using raw pressure however will be the most accurate way to calculate your ballistics. Also make extra sure your 300 yard zero is really a 300 yard zero and not just close.