I don't have it anymore, but basically here's how:
1. Make two A shaped frames out of three paperclips. Two for each long side of the A, joined by a little loop at the top and one halfway down for structural support. Make all your joints by little loops in the paperclips.
2. Join the two tops of the As with a long stretched out paperclip.
3. Tape the feet to a piece of paper or cardboard for stability.
4. Make the arm with a large strecthed out paperclip. Put the loop that it will pivot on at about 1/4 the way along. Tape to the short end a stack of about 10 pennies. Put a little bit of a hook on the long end.
5. tape a still close paperclip to a penny so that you have a little loop to put on the hook.
6. Put the projectile on the arm hook, pull back and let it fly. You'll probably need to hold the legs or it tends to fall over.
I guess that's a lot more than 4 paperclips.