Crosman Custom velicities

hey everybody,
over the summer i bought a crosman custom shop gun with an 18″ barrel. i also got a 2400 style hipack, because CO2 sucks when it get cold, and my intentions were to hunt euro dove, pigeons, and squirrels with the gun. I just recently downloaded chairgun to my computer, and now have the velocity bug! :angrymob:
i started fooling around with the gun this morning to see what the ark of the pellet exactly is.
now, i have taken pigeons and squirrels reliably with this gun, but my velocity calculations seem very low powered for what, seems to me, the gun is capable of doing.
I got an estimated 430 FPS with an 18″ barrel, running off HPA.
Here are my estimated ranges and holdover:
-1.5″@0.0yds
-0.37″@5
0.27@10
0.39@15
0.00@20
-0.95@25
-2.47@30
-4.57@35
i shot the gun at 25 and 30 yards, and the pellets were right where the table said they would be. am i correct that the gun is shooting 430 FPS? is the “power necessity” for game just lies? or was i just really accurate when shooting at game with an under powered rifle?