I am guessing that JSBs 18gr at about 900 fps is as good as it gets. But others know more than I do. So lets see what others suggest.
This is my favorite setup, it gives you 32fpe which is enough power to hold you way past 100yrds and still maintain accuracy. To me, the most enjoyment I get with my Condor is taking starlings at 100m+ and this is the setup I use. Got 43 last year, hopefully I’ll beat that this year.
H&N 21g 5.52mm