Going under the radar

Up to this point I have invested little time or interest in chronographs. They seemed almost irrelevant to me. A chronograph tells you the speed of your bullet, from that speed you can work out your drop. I’ve always done it the other way around – find out your drop and that gives you a muzzle velocity (MV) to input into your ballistic calculator.

My reasoning has been that I have all the accurate known variables that I need, such as station pressure and air temperature. I had tools to tell me what these variables are on any given day. These tools included my GeoBallistics Weather Meter and my Suunto watch.

I would plug in these atmospherics and use my muzzle velocity that I had reverse engineered by truing my gun. Truing my gun simply means firing at a distant target to see what elevation is required to hit it. The distance of the truing target is chosen based on what range the bullet is nearing the end of its supersonic flight (1126fps) – a projectile is very predicable out to this range.

For my 6.5 Creedmoor that range is about 900m. But what about ballistic coefficient (BC)? The best way for me to get my head around the finer points of BC is to let a rocket scientist figure it out and, thanks to Brian Litz of Applied Ballistics, I now have that info at the tip of my fingers: once again the