Reliable breech-loading naval guns in 1750

How would a reliable screw breech developed in 1750 change naval warfare?

It would greatly raise rate of fire, reshape ships of the line, and accelerate cartridge, ignition, recoil, and projectile technology.

Fleet actions would become much bloodier because guns could be reloaded from the rear without hauling them fully inboard. Ships of the line would not immediately disappear, but two-deckers and thicker hulls might become more attractive than very large three-deckers. The new mechanism would also stimulate early experiments with bagged charges, paper cartridges, percussion ignition, and methods of retaining the projectile in the bore.