That chronograph isn't that highly regarded and I'd suspect the changing light from one day to the next had something to do with it.
Also, how hot was it? I gave up on RL22 a long time ago because it's temp heat sensitive, I watched my velocities climb over 300 fps out of a 7mm rem mag one day over the course of about 20 shots on a pretty warm Mississippi afternoon. I now use H1000 and get a lot less temperature sensitivity. I've seen various degrees of temp sensitivity over the years but have seen nothing as bad as RL22. That was a while ago and maybe they've reformulated it since. I don't use the stuff for anything any more.
