2003 US Army BRADLEY GUNNERY 503p.pdf - Survival Books

FM 3-22.1Figure 2-9. M792 HEI-T.(1) The HEI-T cartridge is a fixed-type, percussion-primed round. The one-pieceprojectile body contains HEI and is crimped onto a steel cartridge case. The hollowedsteel projectile houses an M758 mechanical fuze, 32 grams of an HEI mix, and apressed-in tracer. The projectile is yellow with a red band, black markings, and a gold tip.On some rounds, the projectile's yellow color is slightly orange near the red band.(2) Gasses produced by the burning propellant send the projectile out of thegun at 1,100 meters per second (plus or minus 20 meters per second). On impact, theM758 mechanical fuze (Figure 2-10, page 2-16) ignites and the HEI filler detonates. Thisprojects steel fragments from the body, rotating band assembly, and incendiary filler overa 5-meter radius.(3) The maximum effective range for HEI-T rounds is 3,000 meters, at whichrange, a mechanical fuze (the M758) detonates the round. Accuracy decreases beyond1,600 meters, and the tracer burns out at 2,000 meters. However, the round's 5-meterbursting radius and rate of fire let the firer engage either point or area targets out to themaximum effective range.(4) The M792 HEI-T projectile can detonate in any of three ways: directimpact, grazing impact, and self-destruct (Figure 2-11, page 2-17). The piston and bodyassemblies are forced to aft position by the projectile's acceleration in the gun tube (1).The air is forced from the rear cavity into the newly created forward cavity (2). Air flowsthrough the porous restrictor (3). The spin locks the rotor (4) and causes the seal to fixagainst the wall (5). This forces the ball outward and locks the body assembly in the rearposition (6).(a) Direct Impact. Striking the target crushes the projectile's probe cap. This pushesthe probe rearward, which thrusts the firing pin into the detonator, which detonates theHEI mixture.(b) Grazing Impact. Due to spin decay (loss of forward velocity), the projectilestrikes the target with insufficient force. Spin decay triggers the setback spring toovercome centrifugal force, pushes the body assembly forward, and thrusts the detonatorinto the firing pin.(c) Self-Destruct. If it does not hit a target, the projectile self-destructs at 3,000meters. However, head and tail winds, depending on their severity, can reduce thedistance at which the round self-destructs.2-15