Multiperforated grains

This means that if a proplnt burning in a closed vessel is without perforations(such as cordite), there is no erosion of the grains, but if a proplnt is perforated(as in US single- and multiperforated grains) there is erosion in channels but not on the outside surfaces of grains... 

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

Multiperforated Propellant Grains. See Cannon Propellant or Cannon Powder in Vol 2, C30—31, Grains of Smokeless Proplnts in Vol 6, G123... 

Single- and double-base propellant grains can have various morphologies, including long-, short-, or multiperforated tubes, short rods (macaroni), rings, cubes, flakes, strips, disks, balls, and flattened balls. 

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