Ok, I'll bite. Why would you shoot a turtle?
Turtles destroy stock ponds. Ruin any chance of stocking them.
Last year my mother in law begged me to come down there and clear out the turtles on her two ponds in OK.
Fund shooting, most of the time you only get the little bitty head for a target. Those suckers have some pretty good eye sight also. I had to hide behind some brush.
You certainly can go through some ammo.
I used a 22 (CZ 452 Miliary trainer), never thought about cast bullets. Gonna have to try that next time.