Other mistake: When Rango is loading his revolver during the stand-off, he loads the bullets on the right of the revolver, however, the chamber is hanging from the left of the revolver.
Other mistake: Just as the preacher finishes stitching up Jake's wound, a shot rings out from the street, and everyone goes outside to find Percy Dollarhyde drunk and shooting up the town. Percy is right-handed but holsters his 6-shooter revolver on the left, and this appears to be his only sidearm. Even if he did carry another 6-shooter, that wouldn't explain how he fires 13 shots in this scene without reloading.