Pro Diablo 2 is amazing! I can hit cans with some regularity at 10m and hope to get better with practice. I ordered 1000 9mm steel balls for just £15 from ramsbottoms, that's cheaper than pellets! I have a plan for a rebound-free, ball catching backstop. I may even be able to make one to bring to the bash.
Edit: I have just been told in no uncertain terms that rebound-free or not, it is not welcome in the garden