In the shooting accident, at first the front trigger is pulled and the gun fires. Then the back trigger is pulled and the gun clicks. The gun is opened and the cartridge from the right barrel ejects while the left barrel doesn't: The dud (the 20 caliber cartridge) was in the left barrel. The gun is reloaded, the front trigger is pulled and the gun explodes: The 20 caliber cartridge was now in the right barrel. Later closeups of the gun confirms this.
On the tombstone of the magician's assistant, the name is Claire. In the credits, the name is Clare.