Quote Originally Posted by airgunnut View Post
Speed of the pellet in feet per second, times speed of the pellet in feet per seconds, times pellet weight in grains, divide by 450240. Simples

Where 450240 is twice the gravity constant multiplied by grains per lb. (7000)
You can change the constant accordingly if you weight shot in ounces or lbs.
Another interesting number is 671. Any object travelling at 671fps has a ft/lb power the same as its weight in grains. Ie a 15.6gr AA pellet at 671 is running at 15.6 ft/lb. an 8.4gr at 8.4 ft/lb etc.
so a 5lb cannon ball at 671fps is a whopping 35000 ft/lb, but it will still have the same basic trajectory as the .177 8.4gr pellet.