M825 155mm Projectile
The M825 is a 155mm Smoke projectile used to provide screening or marking smoke. It is a separate loading munition using a hollow forged steel shell. The shape is ogival with a boat tail for aerodynamic efficiency and a welded steel baseplate. Close to the base is a gilding metal drive band protected by a grommet until just before loading.
The M825 White Phosphorus (Felt-Wedge) is a 155mm base ejection projectile designed to produce a smoke screen on the ground for a duration of 5 to 15 minutes. It consists of two major components, the projectile carrier, and the payload. The projectile carrier delivers the payload to the target. The payload consists of 116 WP-saturated felt wedges.After ejection, the WP felt wedges fall to ground in a elliptical pattern. Each wedge will then becomes a source of smoke. The projectile is ballistically similar to the M483A1 DPICM family of projectiles.
Smoke ammunition is a limited asset. Since ammunition requirements vary with each mission, observers should know the amount and types of smoke ammunition available and how many minutes of coverage it can provide. Extensive, planned smoke employment should be coordinated early with firing units to allow for redistribution or requisition of ammunition.
The Field Artillery employment of smoke is based upon two delivery techniques: Quick Smoke or Immediate Smoke. Immediate Smoke is designed to build a immediate screen on a point or small area target of 150 meters or less. It utilizes a normal time limit of 5 to 30 minutes in duration. Immediate smoke is normally fired using a parallel sheaf as a separate mission, or as a follow up to an immediate suppression mission. The initial volley may be fired with shell WP, or a mix of shells WP and shell HC. When firing the M825 projectile all howitzers should fire M825 in the initial and subsequent volleys.
Quick Smoke is used to build a screen 100 to 1500 meters in length, depending on the projectile selected. It may be fire as a pre-planned target or target of opportunity. Targets that are exceed the battery sheaf sizes in length should be pre-planned, due to ammunition constraints and the possible need to segment the target. It may be processed as an Adjust Fire or Fire For Effect mission. Accurate mission processing on pre-planned targets, in addition to meeting the five requirements for accurate predicted fire, pre-supposes a positive correlation between wind direction at the screen location and what is listed on line 00 of the current met message.
The M825A1 White Phosphorus shell deploys 116 WP impregnated felt wedges that provide screening for about 5-10 minutes over a 125-250 meter area that obscures enemy vision or screens maneuvering elements. It deploys about 12.75 lbs of White Phosphorus impregnated felt wedges, and weighs about 102 lbs.
The body of this 155mm projectile consists of a hollow steel shell containing the fill. A fuze adapter is screwed into the body and brazed in place. The agent is added and the burster well is then press-fit into the fuze adapter followed by the M6 Tetrytol burster being installed into the burster well. A fuze well cup made of either aluminum or Bakelite is installed by first coating the lower interior threads of the fuze adapter with sealing compound or cement and the screwing the cup down into the fuze adapter.
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