I have my rifles sighted in at 25 yards and this works well for my small game hunting. Most of my squirrels and rabbits are taken at 30 yards or less, although I have taken them further out, so my small game hunting is far from being a long range sport. As for the effective range like I said, I'll take a 40 yard shot a squirrel, done it many times, and the predator pellets (my main hunting pellet) get the job done cleanly. The crosman CPL's are a good hunting pellet also and should be able to take out a squirrel at 40 yards with a well placed shot.
As for trajectory charts and software,,, I'm sure they are out there, no doubt some of the other members can give you such links. I've never used them so I can't help you there.
After I sight in a rifle at 25 I will then shoot the rifle from closer and farther ranges in order to map the POI and assist me with holdover or holdunder. I keep a folder on each and every one of my rifles. In that folder I document information about the rifle,,, when it was cleaned, sighted in, any alterations I may have made, FPS information and the like,,,,,, I also keep the targets I used to sight the rifle in, the targets I used during my pellet grouping tests, and target shooting targets.
After I take a rifle out of the gun safe to shoot or hunt with it the next thing I do is take the appropriate folder out of the filing cabinet and refresh my memory as to what pellet the rifle is sighted in for, what other pellets have the same POI in case I want to use one of them, and what the holdover is for the particular pellet I plan on using. The information contained in the guns folder assists me in getting maximum performance out of the rifle and thus enables me to hunt more efficiently.
Jeff