Navy

M242 Bushmaster 25mm Automatic Gun..

Sailors assigned to the USS Kearsarge (LHD 3) conduct a live-fire exercise while at sea, Feb. 5, 2013. The 26th Marine Expeditionary Unit (MEU) is aboard the Kearsarge conducting Composite Training Unit Exercise, the final phase of a six-month pre-deployment training program. The 26th MEU operates continuously across the globe, providing the president and unified combatant commanders with a forward-deployed, sea-based quick reaction force. The MEU is a Marine Air-Ground Task Force capable of conducting amphibious operations, crisis response and limited contingency operations. Video by Lance Cpl. Juanenrique Owings | 26th Marine Expeditionary Unit

The 25mm M242 Bushmaster cannon used on the Bradley Fighting Vehicle and a variety of land and sea vehicles. The Marine Corps carries this weapon on the Light Armored Vehicle (LAV) while the Navy carries it on many of its ocean-going vessels to deal with small attack craft.

The M242 25mm “Bushmaster” Chain Gun, manufactured by McDonnell Douglas, has a single barrel with an integrated dual-feed mechanism and remote ammunition selection. Either armor piercing (AP) or high explosive (HE) ammunition may be selected with the flick of a switch. The Gunner may select from single or multiple shot modes. The standard rate of fire is 200 rounds per minute, and has a range of 2,000 meters (depending on the ammunition used). A wide range of ammunition has been developed for this weapon, making it capable of defeating the majority of armored vehicles it is likely to encounter, up to and including some main battle tanks. The M242 25-mm, fully automatic, externally powered gun can destroy lightly armored vehicles and aerial targets such as helicopters and slow-flying aircraft.

It can also suppress enemy positions such as troops in the open, dug-in positions, and built-up areas. The 25-mm automatic gun mounted on the M2/M3 Bradley fighting vehicle offers infantrymen an effective weapon for urban combat. The primary role of the BFVs during combat in urban areas is to provide suppressive fire and to breach exterior walls and fortifications. The wall and fortification breaching effects of the 25-mm automatic gun are major assets to infantrymen fighting in urban areas. The 25-mm gun produces its best urban target results when fired perpendicular to the hard surface (zero obliquity). During urban combat, however, finding a covered firing position that permits low obliquity firing is unlikely, unless the streets and gaps between buildings are wide. Most shots impact the target at an angle, which normally reduces penetration. With the APDS-T round, an angle of obliquity of up to 20 degrees can actually improve breaching. The rounds tend to dislodge more wall material for each shot but do not penetrate as deeply into the structure. Reinforced concrete walls, which are 12 to 20 inches thick, present problems for the 25-mm gun when trying to create breach holes. It is relatively easy to penetrate, fracture, and clear away the concrete, but the reinforcing rods remain in place. These create a “jail window” effect by preventing entry but allowing grenades or rifle fire to be placed behind the wall. Steel reinforcing rods are normally 3/4 inch thick and 6 to 8 inches apart-there is no quick way of cutting these rods. They can be cut with demolition charges, cutting torches, or special power saws. Firing with either APDS-T or HEI-T rounds from the 25-mm gun will not always cut these rods. The 25-mm gun more easily defeats brick walls, regardless of their thickness, and the rounds produce the most spall. The 25-mm gun is devastating when fired against sandbag bunker walls. Obliquity has the least affect on the penetration of bunker walls. Bunkers with earth walls up to 36 inches thick are easily penetrated. At short ranges typical of combat in urban areas, defeating a bunker should be easy, especially if the 25-mm gun can fire at an aperture. Although the penetration achieved by the two combat rounds-armor-piercing, discarding sabot with tracer (APDS-T) and high explosive, incendiary with tracer (HEI-T)-differ slightly, both are eventually effective. However, the best target results are not achieved with either of the combat rounds. At close range against structural targets, the training round (TP-T) is significantly more effective. The TP-T round, however, has little utility when used against enemy armored vehicles. The APDS-T round penetrates urban targets by retaining its kinetic energy and blasting a small hole deep into the target. The APDS-T round gives the best effects behind the wall, and the armor-piercing core often breaks into two or three fragments, which can create multiple enemy casualties. The APDS-T needs as few as four rounds to achieve lethal results behind walls. When firing single rounds, the APDS-T round provides the greatest capability for behind-the-wall incapacitation. The APDS-T round can penetrate over 16 inches of reinforced concrete with enough energy left to cause enemy casualties. It penetrates through both sides of a wood frame or brick veneer building. Field fortifications are easily penetrated by APDS-T rounds. The APDS-T round creates a hazardous situation for exposed personnel because of the pieces of sabot that are thrown off the round. Personnel not under cover forward of the 25-mm gun’s muzzle and within the danger zone could be injured or killed by these sabots, even if the penetrator passes overhead to hit the target.

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