the stealth artilery method[}:)]
get 4m(aprox.) of 100-125mm poly piping
drill 4 holes about 6mm dia 15mm in from one end
mount 4 sets of thick rubber bands or thin jelly rubber(about 200-250mm long)
mount a pouch big enough to hold a cricket ball
now find a spot within 100 to 150m with some thick bushes to hide in
fill pouch with handfull of pea gravel (6-10mm dia best)
aim now fire your rain of terror on to little b*%^&rds
yes I had a lot of fun as a 12 year old