I recently purchased a Howell 45 Colt conversion cylinder for my Pietta replica 1858 Remington black-powder revolver. I have a question that wasn't covered in the instructions that came with it. The cylinder has a seventh locking slot positioned about one third of the way between two of the normally spaced other six. I was wondering about its purpose and proper use. The cap-and-ball cylinder it replaces has no such extra slot.