Progressive ratchet rifling in a full gain twist

In a barrel having rifling running from beginning to end of a portion of the bore and including surfaces defining lands, and grooves, the lands having respective leading edges for guiding projectiles and trailing edges and tops the improvement comprising in combination:

• at the beginning each land having in cross-section a relatively narrow and shallow rectangular shape with the leading and trailing edges relatively equal in depth, said rifling being at the beginning relatively parallel with the bore and running forwardly therefrom in an accelerating spiral;
• and concurrently with said forward running each groove surface rotating in a direction increasing the depth of the leading edge of a land adjacent to a first side thereof and decreasing the depth of the trailing edge of a land adjacent to a second side thereof until at said end the trailing edge and top of each land are merged with an adjacent rotated groove contour.