Randall, thanks! That makes sense. I hadn't thought of checking their respective BC's.
I have one other question your reply brought up in my mind.
You wrote, "I'm shooting 155 SMK's at 2875fps and I still have some margin to warm up the load some more."
How do you know how much further you can push your load? Is the pressure generated by the load combination (bullet, powder type, powder charge, etc.) the main determining factor of the safety margin?
Are you using a ballistic program to help determine how fast you can push the 155 Scenar before getting into the danger zone?
I've been working up my loads with the data from a couple of sources of loading manuals, powder manufacturer data, etc., and I then chrono my loads as I work them up. I've been well shy of max loads, but I have no real idea of what the pressures of my loads are. I've just been going on the the info from the loading manuals, and trusting that since I am well below max loads, and in the case of 168 SMK, I am dialed in to right around 2650 - 2680 fps, that I am okay in the safety department.
I'd love to have a ballistic program, but being a Mac computer guy, I'm not sure there's really anything available. I really don't want to load Windows on my Mac, so that's not the solution for me.