The M4A2 (white bag) Propelling Charge is a separate loading charge used in 155mm howitzers for firing in Zones 3, 4, 5, 6, and 7.
The full M4A2 Propelling Charge consists of 13.4 lbs (6 kg), of M1 propellant and is divided between a base charge and four unequal increments loaded in white cloth bags. The increments are connected by four cloth tapes sewn to the base and tied on top of increment. The igniter contains clean burning igniter (CBI) in a red cloth pad sewn to the bottom of the base charge. A flash reducer pad containing potassium sulfate or potassium nitrate is installed at the front end of the base pad (Increment 3). The seams in the base pad are inverted so that the edges of the cloth are inward to reduce residue after firing.