Introduction: Working Lego Technic Revolver
A working LEGO revolver, with full instructions.
Step 1: Handle
Step 2: Barrel
Step 3: Connect Them
For loading, put the ammo (Part No. 5003235-1) down the barrel, rotate the cylinder to seat the ammunition in place, repeat until the cylinder is full.
If anything is unclear post in the comments and I'll try to clear it up.