I have some RL19, so I could do a quick velocity run up to see what it does the next time I am able to experiment. I really think I am getting to the point where Quickload would be very useful. I am planning to add that tool to my arsenal and see what it spits out. I am also contemplating a Magnetospeed
chrono to make things easier.
I am glad to encounter another interested .375 shooter. There can't be enough of us to my way of thinking. I apologize in advance for the slow pace of my experiments. I only have a small window of opportunity to continue them every few months.
I will continue to post results as development continues. When I have something meaningful (like a finalized load), I will post photos.