Will O’Meara puts his projectiles through a variety of vigorous tests, hoping to find the secret to true accuracy
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 Ballistic Arc App proves its worth with its multiple BC solution. This gives you three BC values for a projectile.
The science behind this is basically that the BC of a bullet will change during its flight depending on the speed that it is travelling.
For the Sako Gamehead Pro this BC Profile looks like this:
This shows me (and tells my ballistic software) that as the bullet slows down the BC value drops. Luckily all this is calculated by magic inside my phone on the Ballistic Arc App!
So that leaves us only with the velocity part of the puzzle. I decided it was time to broaden my horizons and learn more about the true value of accurately gauging the speed of my bullet. My early experiences of chronographs highlighted the finicky nature of these speed metres. They were awkward to set up, needed a nice sunny day (a rarity in Ireland) and seemed to be bullet magnets due to the fact that you had to shoot through them. Nowadays we have tools such as Magneto-Speed and Labradar to give us consistently accurate readings.
For the testing conducted
