Has anyone seen errors when using the BC function in the Hornady app? It gives correct readings when using 4DOF but the ballistic calculator is significantly off. This has happened the last two times I’ve been gathering dope on new guns.
And yes the selected bullet and variables are the same.
BC is an approximation that needs to be calibrated to reality. AB’s custom drag curves and Hornady’s equivalent (the 4DOF stuff in the app) are better approximations but still aren’t going to be 100% perfect.
4DOF was very accurate in this instance. Right on the money at least to 500 yards.
Yeah but at a fundamental level these models work by applying a drag curve to your velocity and extrapolating how much it slows down and falls to the distance you select. A G1 or G7 standard curve is an average curve that assumes that all bullets of a certain type have a very similar profile (G1 is for flat base bullets, G7 is for HPBT, and the fact that manufacturers stick G1 BCs on other kinds of bullets is dumb). In reality there are a lot of differences between different manufacturers’ bullets and the BC is mostly useful as a comparison between how well those bullets perform on average, but will be off for every individual bullet. Hornady and AB have taken radar measurements of individual bullets to make a custom curve for each one that is much closer to reality, but because the dies to make the bullets age and the manufacturers can make adjustments to the design of the ‘same’ bullet, it doesn’t necessarily mean that these are perfect either.
Hornady has a couple of great podcast discussing this. I don’t know if Litz has anything online, but he’s also written about it in his books.
Why we are still using a G1 BC for modern bullets is indeed stupid. Guess it’s because a, it’s what everyone is used to, and B, this is America and we want our numbers big.
I prefer Geoballistic the new version has a lot of great features.
