It’s not just FPS, it wouldn’t matter if you were throwing those tiny light pellets out at 1200 fps. There’s a huge weight difference. Weight or similarly (though not the same) mass times acceleration = force. Typically measured in Newton meters (Nm) or foot pounds (ft/lb). A 15 grain pellet moving at 1200 fps would be roughly 65 Nm or 48ft/lb. An 18gr pellet would add about 10ft/lb or 13Nm to that number. It’s no where near a 40 grain 22lr moving at 1200 fps (roughly 162 Newton meters or 120ft/lb). Decent subsonic 22lr is going to be moving about 1037fps. With a 40gr bullet that’s still 96ft/lb or 130Nm. As fancy as many pellets are these days, they still don’t compare to real ammunition in terms of expansion, design or devastation. Even the ancient 22lr “hollow point” design is going to expand better and dump all its energy more efficiently than most expensive hunting pellets, because there’s just not enough oomph there.
