Originally Posted by _cy_
read their inflated claims??? ... 1,500 fps with worthless alloy pellets .. ya right
so what's the real life speed with pellets (.177 or .22) one can actually hunt with?
A robust, spring-piston, break-action system gives you the power to drive .177 alloy pellets at a potent 1500 feet per second.
In general you try to keep the pellets under 900 fps for accuracy. You certainly do not want to shoot at 1000 fps or higher, which some manufacturers advertise as an asset in stead of the liability that it is.
For spring guns in .22 that velocity is usually lower still, because a springer that shoots at very high energy (pellet weight x velocity^2 ratio) can be harsh and hard to shoot accurately consistently.
Just recently there was a thread on yellowforum.com
where someone was having accuracy problems (had flyers causing group side to open to golf ball size at 50 yards). Dropping the pellet speed from 920 to 870 fps made the gun shoot much more accurately, one ragged hole at 40 yards.
So to answer your question:
Whatever pellet speed your rifle shoots most accurately.
There is no significant "hydrostatic shock" at airgun muzzle energy, so shot placement is everything. Many argue that .22 pellets anchor their prey better than .177 given the same accuracy. But you can't go around smacking a squirrel somewhere in his body and expecting it to die instantly or even quickly. A brain or heart/lung shot is essential, especially in this particular example, squirrels seem descendants of a zombie father and an Abrams tank mother.