Pressure activated inertially locking base for projectiles

A method of extending and locking fins upon firing of a projectile from a weapon barrel, the method comprising the steps of:

• (a) providing said projectile having a housing with a base, and with a base portion extending from said base, the base portion containing a plurality of slots penetrating and extending into said housing, each slot having a top and bottom, the top being located on the side of the slot closest to the nose of the projectile, and the bottom being located on the opposite side of the slot closest to the base of the projectile;
• (b) stowing within each slot a fin, each fin mounted to the base so as to rotate about a pivot point to move to a deployed position, wherein said fin extends from said housing to help stabilize the flight of said projectile;
• (c) and wherein said pivot point is located near the bottom of each slot and toward the outside of the slot;
• (d) and wherein the center of gravity of each fin is such that it is stable in such a stowed position;
• (e) providing a plunger which has a lower side which is aligned with and seals the base of the projectile prior to firing thereof and which plunger has an upper side, at least a portion of which is in communication with a chamber;
• (f) providing a plurality of relatively small passages through said plunger that allow pressure communication between the lower side of the projectile base and a said chamber;
• (g) firing said projectile, such that said chamber is pressurized thereby;
• (h) whereby, upon the projectile exiting the barrel, a pressure differential is created between the chamber and the lower side of the plunger, such that the plunger extends from the base of the projectile, causing a set of spring arms to contact and motivate the fins to rotatably deploy from the slots;
• and
• (i) whereby, once the fins are deployed, a spring loaded pin, which had been blocked from movement by the stowed fins is freed to move, and does move to a position behind the fins, to lock the fins in the desired deployed position.