Rockinbbar,
That's my 9th cat, and was the largest one I have taken so far. It weighed 27# - not as big as some I hear about, but a nice cat for my area.
You are right about the cartridge (6x45) not doing much damage. I shoot 75 gr. Sierra HPs. They penetrate really well, put cats and coyotes down, and don't blow everything into eternity. Usually the exit wound is about quarter size or thereabouts, sometimes a little larger.