Depends on the barrel twist, I have a 1:12 and shot the 53gr Hornady vmax at 3700 fps and group .380 @ 100 yards. Rabbits and 'Yotes die if I do my part. If the gun has a 1:9 or faster, go with a 55 grain or heavier bullet. If it is 1:10-1:12 stay in the 45-55 range, 1:14 then the 30-45 grain bullets will work.
But I also like to try every brand, every weight to see what is best.