Charlie has a crippled walk which comes and goes throughout the film.
Carl Oliver's position against the car in the first scene with Charlie changes between shots. He varies from being against the fender near the engine bay to being next to the driver's door.
When Charlie taunts Ed about whether the gun is loaded, he fires a shot into the ground, challenges Ed to attack, then reloads and says the gun was empty and that Ed missed his chance. However, a Colt M1911 will lock the slide to the rear when the last shot in the magazine is fired. But this pistol went into battery (loaded another round). That means there was still at least one round loaded in the chamber. It's possible Charlie was lying about the gun being empty to taunt Ed further, but in either case Ed was smart not to attack.
After Charlie is doused with gas by Ed, he fires his revolver seven times in a row. The maximum rounds in a revolver of that era is six.