Perforated grains

Perforated Grains (Propellants). See under Camion Propellant or Cannon Powder in Vol... 

An advantage of the smokeless powders is their ability to be extruded during the manufacturing process. Perforated grains can be produced that simultaneously burn inwardly and outwardly such that a constant burning surface area and constant gas production are achieved. 

British, German, Italian, Russian and Japanese proplnts examined at Picatinny Arsenal during WWII included squares, perforated discs, single-perforated tubes, single perforated grains, multi-perforated grains, spheres and strips. The basic idea behind the use of the varied forms is connected with the desire for a propint with a... 

Fig. 187. Modes of burning of perforated grains and cords. The dotted lines represent approximately the positions of the inward and outward burning, according to [25].

Powder for rockets is usually in the form of perforated grains with a large diameter, considerably larger than that of the tubes used for cannon charges. This makes the production process for extruding the powder mass very complicated. 

All perforated grains, especially multiperforated ones, burn progressively because the burning surface of the grain increases as the grain is consumed... 

As to the web thickness, the larger the value, the slower is the proplnt. For single -perforated grains, as most US small arms proplnts are, the web thickness is equal to half the difference betw the outside diam(such as 0.049") and the diam of the perforation such as 0.015")... 

Note Accdg to L.Shulman ofPicArsn, this app can be used only for "nonperforated grains (such as used in rockets). It cannot be used for "perforated grains (such as used in cannon proplnts). This is because the flame would go down the perforations and... 

Rodman, U. S. Army, discovered the principle of the progressive combustion of gunpowder and proposed perforated grains in prismatic form. 

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