Solid propellant grain for improved ballistic performance guns

Claim 1

A solid propellant grain structure having a smooth exterior surface comprising: a longitudinally extending, progressive externally burning grain having a generally hexagonal cross-sectional shape, said grain having six flat outer surfaces joined by rounded longitudinal edges; a plurality of spaced equally sized longitudinally extending throughbores formed in said grain wherein an optimum throughbore configuration includes seven throughbores along a line connecting diametrically opposite edges, said throughbores including; perimetric throughbores positioned adjacent said longitudinally extending flat outer surfaces; and internal throughbores positioned so that interstial distances between adjacent perimetric and internal throughbores are substantially equal, and wherein extrastitial distances between each of said perimetric throughbores and the normally adjacent longitudinally extending outer surface of the grain are substantially equal to said interstitial distance, which includes; each of said rounded longitudinal edges having a radius of generation equal to one-half the diameter of said internal and perimetric throughbores plus the value of said extrastitial distances; said substantially equal interstitial and extrastitial distances promoting more nearly simultaneous and uniform ignition and improving burning characteristics of said grain by maintaining higher average pressures and velocity during projectile acceleration without increasing maximum pressure.