too late for me to guess, but I wasn't going to anyway.
What I was going to say is that my experience with chronos and several guns and loads is that the data in the loading manuals is pretty close, and individual guns will show individual differences. I have see as much as 100fps above, and below the published data from different guns, although usually it is much less. Rarely it is spot on, but that, I think is just serendipity.