XM1018 High Explosive Air Bursting (HEAB)
The key to delivering the revolutionary increase in lethality and survivability of the Objective Individual Combat Weapon (OICW) was the precision XM1018 High Explosive Air Bursting (HEAB) ammunition. It consists of a center-body fuze with a controlled fragmenting warhead on each end. This design was chosen to maximize lethality. This is a very challenging system to develop and test but was successfully demonstrated multiple times. The key technologies and integration drivers being addressed included miniaturized and gun-hardened fuze electronics, ammunition reliability, a "man-rated" safe and arming system, system interfaces between the weapon, fire control, and ammunition, dual warhead lethality, uniform ammunition propulsion, and weapon recoil mitigation. What makes this system unique is its ability to provide all-electronic information on range, to automatically adjust the aim point, and to inductively set the fuze in the chambered round automatically. All the soldier has to do is aim, lase, adjust his/her aimpoint, and fire; the calculations are transparent to the user.
The HEAB munition will have a settable fuze that interacts with the TA/FCS automatic fuze programming. It will have the necessary lethal radius to insure the required P(i) s are met. The HEAB munition shall demonstrate a minimum reliability of not less than that of the current 40-millimeter M406 HE/M433 HE Dual Purpose (HEDP) cartridges. A family of cartridges for the HE portion of the weapon will be developed including an inert cartridge for training, a target practice spotter cartridge which indicates actual burst location, and a blank cartridge for force on force training.
The HEAB round will have a maximum range of 1,000 meters and must provide a probability of incapacitation P(i) of not less than 0.5 at 500 meters against an exposed point target, and 0.35 at 500 meters against defilade targets.
The 20mm ammunition designed for SABR provides the lethal link in the sensor-shooter-target chain. Developed by the system's prime contractor, ATK Integrated Defense Systems, the 20mm airburst high explosive ammunition was successfully test fired in January 2002. The 20mm HE grenade is about the diameter of a nickel, measures 3 5/8" long and weighs 3 1/4 oz. Advances in miniaturization technology have enabled the production of tiny, multifunction, remotely programmable fuzes. Once the SABR operator has determined the range to the target and input the desired firing mode, the FCS programs the fuze inside the chamber of the 20mm barrel, using signals delivered by an induction coil. The round, spun by rifling in the barrel, counts the required revolutions to the target, and detonates as programmed. In theory, the system could be programmed remotely using information from battlefield sensors, and fired by an operator who is securely behind cover . The programmable fuze results in dramatically enhanced lethality against the types of targets most often encountered on the battlefield: targets either behind cover or, increasingly, within buildings.
The pre fragmented high explosive warhead is designed to defeat lightweight body armor and light cover, at effective range of up to 1000m. Plans call for a target cost of $25 per round of ammunition.
In tests concluded in January 2002, over 180 rounds of ammunition were fired to confirm air burst accuracy, system safety, and environmental assessment at ranges of 100, 350 and 500 meters. The testing verified the ammunition passed all safety requirements, leading to an "okay to proceed" from the Army Fuze Safety Board. In addition, multiple operational modes and functional capabilities were demonstrated, including precision turns count fuzing, point detonation, self-destruct, and short arm. The short arm mode provides the soldier a unique capability for the MOUT (Military Operations in Urban Terrain) environment. Further, the fuze provides for self-destruct and self-neutralization to provide a safer battlefield for the infantry as they move forward.
Early in the 2002 the XM-29 weapons were successfully tested with the new 20mm HEAB (High Explosive Air Bursting) munitions. But the 20mm smart grenades did not seem to be lethal enough in subsequent testing. Following the increase of the caliber of OICW grenade launcher component from 20mm to 25mm [the same as used in the OCSW], in July 2004 it was decided to split the OICW system into two separate weapons, the 5.56mm XM8 modular assault rifle (OICW Increment 1), and the 25mm XM25 airburst assault weapon / grenade launcher (OICW Increment 2).
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