As can be seen in
@kyron4's post, what you are seeing is a chambered breech. there is no need for rifling as the ball can't get into the chambered breech. The real benefit of a chambered breech is in the manufacturing process. Only one type of barrel needs to be inventoried. All the barrels can be threaded for the threads of the chambered breech. An unintended consequence is that there is more material at the breech to contain the pressure of ignition. The manufacturer can have four types of chambered breeches in inventory. Flint breeches, percussion breeches, and right and left breeches. With a bit of planning, a touch hole liner and a flint drum can have the same threading and only two breeches need to be in inventory.
Patent breeches are a far more complicated design. Actually, only Nock's design can be truly called a patent breech. The theory is that the powder in the antechamber by the touch hole ignites and sends a strong jet of flame into the powder charge. In some of Nock's designs, there is a tiny relief hole with the theory that the relief hole provides a pathway for the heat from the pan ignition to flow through the powder charge in the antechamber for faster and improved ignition. In practice, it does work with the strong jet of burning powder keeping the chamber and antechamber mostly clear of fouling. No current factory production utilizes a Patent Breech system as designed by Nock.