Small charges from large bores can be very effective and fun.
Some years back, my buddy Keith and I did a bunny hunt one March, on snow-shoes for hares. Keith used his .75 Sporting rifle with 45gr. 2F GOEX and I used my .69, with 30gr. 2F GOEX, both of us shooting patched round balls.
Due to the low velocity, you could hear the head bones crunching apart from the sound of the gun. The range was usually 30yards or closer.
This SxS .577 will be a fun gun for this sort of "plinking".
Fun, fun!