A friend and I were shooting the other night, started at 200 to make sure all was good. It was switched to 400 in a different spot and we were both 7 inches high. It was dead calm and the night air was starting to come in real cool and we were shooting over ground that had the sun on it all day other than that i cant think of any unique circumstances. I also could see the vapor trail when he shot and it looked like it had a lot of arc in it. Any ideas?