Choosing an Airgun for Hunting
If using open sights, you should look for a gun with fully adjustable sights. If using a scope or red dot, make sure that the scope mount is solid. Beginners are encouraged to start with open sights before graduating to scopes.
Where do you plan to hunt? In some locations, there are limits on the muzzle velocity or energy. Make sure that you follow the laws, you'll get caught sooner or later if you break them. Don't use too powerful a gun in residential areas if their use is permitted. Remember, if you have a privilege, use it - don't abuse it. Much of the negative feeling toward our sport comes from trigger happy idiots that don't care about the consequences of their actions. Don't ruin things for the rest of us!
Power is contingent on two things: mass of projectile and velocity. Remember studying about energy in physics? Kinetic energy, or the energy of motion is equal to 1/2 x mass x velocity squared. If you double the mass, you double the kinetic energy. If you double the velocity, you quadruple the kinetic energy. Let's see how this works:
Take your average department store .177 pellet gun. It will shoot a 7.6 grain (gr) pellet at 550 feet per second (fps). This yields 5.1 foot pounds (ft-lbs) of muzzle energy. Not bad, if you are hunting small pests. If you take a RWS model 350, which advertises a 1250 fps velocity, you will get an impressive 26.4 ft-lbs of energy with the same pellet. That will reliably bring down rabbits and squirrel.
Muzzle Energy Calculator