Had something happen to me yesterday that I haven't seen in my 10 years of reloading. Took a new gun out to break it in and followed a 5 single shot between cleaning and then 4 sets of 3 shots between cleanings. I was using the same powder charge the whole time. Temperature was 67 degrees that day. Then yesterday, 60 degrees, I did some scope dialing testing and leveling with the same powder charge and my F1 chrony said I was 100 fps slower than the previous outing. I did open a new can of powder for the last outing but I have never seen a 100 fps variance between lots of any other powder I use. The weather was very similar, sunny and warm and I used the diffusers over the sensors both times. Seems to me that it would be a chono issue vs powder. Anyone run into this before? Maybe the chrono needs a new battery?? I've been frustrated with the F1 but can't bring myself to pay a whole lot for another system or the magneto speed which is trading accuracy information for velocity. Been toying with getting another F1 and putting them back to back.