Check out my Website for all my Lego Guns http://sites.google.com/site/bblegobrickworks/
Check out the youtube video of the A-1 shooting some cans:
Step 1: Underside
This is the first part of the underside of the gun. Note that the next steps pretty much just build onto this, opposed to making seperate parts and putting them together
Step 2: Overside
This is very easy to do
Step 3: Sight
Easy sight to build, very accurate.
Step 4: Trigger
This trigger is the same one as my C-2 Crossbow
Step 5: Rubber Band Holder
Step 6: Rubber Bands + Handholds
Pretty easy. Try and use the pink rubber bands, they are good at firing, and are strong
Step 7: Ammo and Loading
The ammo is a 2x2 brick, with a flat piece on top.