45 grains of varget should get you about 3,900'/sec but I haven't found it to increase range....it just does a splendid job on targets under 250 yards

I use it for the "mist"...not the improvemnent in range.

I use 53 gr. H380 for my 55 gr. BT and .243, get around 4000fps and 1/2" accuracy at 100 yds., my longest shot was 646 paces, no range finder at the time, shot a varmint and it blew a quarter sized hole right through it! I've shot some yotes with it and if you hit them in the rib cage it usually won't come out, but if it does you might as well keep shooting at it for target practice because you'd spend hours sewing the hole together. But don't get me wrong, it's my go-to varmint load.
Yardbird