Load the Colt Python.
Fire a few shots, leaving a few bullets in the weapon.
Right-click on the weapon in inventory to verify that there is no options other than "inspect".
Try drag and dropping more bullets onto the gun in inventory to verify it can't be filled up to full.
Put the gun in "hands"-slot and from there drag and drop the bullets on ground or into inventory.
Try combining the unloaded bullets with a small stack of bullets that have not yet been loaded into the weapon.