i had an s410k cracking guns
as for .177 you need to be a bit more accurate with your shot placement, you can get away with a bit more with .22 because of the bigger round delivering more kinetic energy, more stopping power. but the s400 is amazingly accurate, so shots to the brain at sensible ranges should be easy to achieve
i think hunting with .177 is fine, some may disagree, but if the pellet hits the right spot then the rabbit dies. simple.
dont forget some pics when you have a new scope on it
all the best, SKoT