Thread: "Trueing" BC/Velocity

If you are running a pretty std velocity for the bullet ie a 140 6.5 where you are in that 2750-2900 fps then the BC in your app will be pretty right and just adjust the velocity to correct your drop. If you happen to be running it in a caliber that is going quite a bit faster then you might increase bc slightly and if going a lot slower ie in a Grendel or very short barrel then you would drop the BC. Some bullet manufacturers like Sierra have banded (different velocity thresholds) BC listed. Using a good app with good actual bc data like Applied ballistics BC are more accurate. Running some apps where they use the manufacturers no.s like nosler or Barnes where they maybe slightly over stated you may need to adjust. For std hunting we usually shoot 800m and use that drop for adjusting velocity. Some apps allow you to put in actual drop and will work out velocity for you. Snipers hide has a new app called gravity balistics that will do your dope without using velocity or BC and uses a multiplier but you need targets every 100m. You can true your drop at 600m. Works fine, the closer to your transonic about 1400 fps the better for further accurate drop prediction. Make sure settings are all correct such as scope height above bore and zero range as those 2 factors make a difference. Once getting out to distance atmospheric inputs on day of doing data may make a bit of difference when you shoot again also. Aswell as shooting direction as shooting north south makes a windage error and east west makes a elevation error. Depending on whether your app has a calculation worked in for that. Inside 500m a lot of these factors are minimal. I like to write my drop data in a book when truing a rifle so I can reference if I have trouble with an app or get another one and want the correct inputs.
We do run shooting schools at Sparrowhawknz that teach this, check out the website.