Actually sounds a little slow, Greg, but I'd be interested in what kind of numbers you get for a 30 shot string. A lot of times, these things prefer something less than a 3K fill, and will start slow but then speed up as the pressure comes down. Wish I could be specific, but I never saved any chrony data with the 12" .22 barrel, I was usually shooting either the 12" .177 or 24" .22. TH seems a little big, what's your PW set at?
Do you have MS Excel available? If so, I have a nice spreadsheet set up for 2 30 shot strings, once the data is entered, hit one button and it produces a line graph. I still need to do a little tweaking on it, it currently auto selects the graph range, and I'd prefer it to use the same range all the time. Makes the graphs more consistent. But if you can use it, I'll email you a copy to play with. I've got my Beta chrony set up for 30 shot strings, someday I'm going to upgrade to a Gamma :-). Let me know.
Dave