+1 on the Super Mag. They are my go to pellet for testing a new .177 at 25 yds and carry nicely to about 40. CO2 guns - both rifle and pistol - absolutely love them. They seem almost magic at treetop distance. Have headshot squirrels with a .22 RF, only to have them drop to the ground and run for a hole. But I have never lost one that was headshot with a 9gr. Super Mag.
True story: About an hour ago I was talking to a friend who went squirrel hunting today. His partner was using a 3 1/2", 12 ga load. He peppered a squirrel with three shots and it didn't drop. My friend was using a stock Disco with 2 1/2X short scope and .177 Supermags. His squirrel dropped with a single shot.
Give them a chance in the woods. You may be surprised.