There has been a lot of debate as to whether or not the FX True Ballistics chrono calculates accurate BCs and range cards. I took mine to the Utah desert in 90-degree weather on Saturday at 1,760 yards (24" square target) with my 375 Cheytac. The FX gave a solution that was within one-tenth of a mil off right on and I had impacts starting with my second shot. The one-tenth off could have been shooter error for that matter. So....sample of one but the FX works for me. It is totally my go-to chrono, even ahead of my Garmin.