25 × 59 mm

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25 × 59 mm
XM1050 TP and XM1049 HEDP, in the background the Objective Sniper Weapon
general information
caliber 25 × 59 mm
Sleeve shape rimless with pull-out groove
Dimensions
Sleeve shoulder ⌀ approx. 26 mm
Sleeve neck ⌀ approx. 26 mm
Floor ⌀ 25 mm
Cartridge bottom ⌀ approx. 26 mm
Sleeve length approx. 50 mm
Cartridge length 138.5 mm
Weights
Bullet weight 141 g
total weight 174 g
Technical specifications
Speed ​​v 0 425 m / s
Max. Gas pressure 275 bar
Lists on the subject

The 25 × 59 mm ammunition was manufactured by Primex Technologies (now General Dynamics Ordnance and Tactical Systems) for the Objective Crew Served Weapon (OCSW), also known as the XM307 , and the Objective Sniper Weapon (OSW), also known as the XM109 , developed. The grenade was designed to detonate with impact or air ignition in order to develop an optimal effect depending on the target situation. Although both the OCSW and the OSW including the grenades were developed for series production, they were not procured.

history

The development of the ammunition began in 1995 with the specification of the OCSW. It was determined that the weapon had to fire 25 mm ammunition with at least 250 rounds per minute, up to an effective range of 2000 meters. General Dynamics Armament and Technical Products was commissioned to develop the 25mm weapon along with a tripod mount. Primex Technologies was the main contract partner of the Department of Defense and responsible for the integration of the systems. In addition, Primex Technologies was mainly responsible for the development and manufacture of the 25mm ammunition. The Kaman Dayran company was also involved in the project and developed the firing mechanism for the grenades. In 1999 unmanned firing tests were carried out for the first time with the one-man and two-man versions of the OCSW. In June 2002 further shot tests followed at the Aberdeen Proving Ground . In 2004 the OCSW finally achieved all specified parameters.

The Objective Sniper Weapon (OSW) came only as a career changer to the 25 mm ammunition. After the project was originally open to technology, the anti-materiel capability was given more weight due to the requirements of the US Special Forces. The Joint Service Small Arms Program (JSSAP) then carried out fire tests in 2002 with the 25mm prototype of the Objective Sniper Weapon, which was compared to a Barrett M82 . The OSW performed better, especially over long distances, only about half the amount of ammunition was used. In early 2004, Barrett Firearms Manufacturing, Inc was commissioned to improve the weapon’s performance and recoil, and to build 10 improved prototypes. These were delivered to the Army in August 2004. Within the next six months, the weapon was to be further developed in order to be able to fire air-igniting ammunition . Likewise, all types of ammunition in the 25 × 59 mm caliber should later be able to be fired. In 2006, the weapon was waved along with the Barrett M107 and Barrett XM500 as an anti-materiel payload rifle by the United States Congress, but there was no procurement.

After the consumer expressed doubts about the effectiveness of the XM1018 grenade of the HK XM29 , the OICW program was divided into three parts in 2004. OICW Increment I was supposed to introduce a modern assault rifle into the force ( HK XM8 ), and OICW Increment II was supposed to produce an airburst grenade launcher ( HK XM25 ). The XM25 uses the same 25 × 59 mm shells, but with a shorter case, so that only a muzzle velocity of 210 m / s is achieved. To distinguish these grenades are referred to as 25 × 40 mm . In July 2007, ATK also took over the development of the 25 mm grenades after the company was already responsible for the OICW's 20 mm grenades . The ignition unit of the 25 × 40 mm grenades has a similar structure, but not identical.

overview

Air detonation of a 25 mm HK XM25 shell . The rear igniter means that the sides and rear are almost free of splinters.

The effectiveness of grenades depends solely on the splinters they send out. The faster and heavier these are, the greater their destructive power. The more numerous these are, the higher the hit rate at a greater distance. In practice, this results in a conflict of objectives because the volume and surface area are limited: a thicker wall increases the mass of fragments, but reduces the volume of explosives. Larger fragments allow a constant volume of explosives, but reduce the number of fragments. As a result, an explosive that is as powerful as possible and a wall material that is as heavy as possible is the best choice, but cannot always be realized for reasons of cost.

Secondly, the structure of the projectile is also decisive: the intrinsic speed of the rear fuses results in a forward-facing, conical splinter pattern. The side and the rear area are almost splinter-free. In the case of head detonators, the fragment image is inverted. Here a cone-shaped area in front of the floor is almost free of splinters, but the side and rear areas are affected. Depending on the target location, one or the other structure can be advantageous: For people outdoors, rear fuses are more advantageous, the grenade then detonates shortly before the target, which is hit by the fragment cone (left picture). In the event of impact ignition, the effect on the hit object is better. Head fuses are better for enemies in cover, as people standing at right angles to the flight path, for example behind an obstacle or window frame, can be hit more effectively. In the case of contact ignition, on the other hand, the environment can be better split up.

The detonator position of the 25 mm grenades was subject to constant change during development: If the initial concept still provided rear detonators for all variants, the detonator unit of the high-explosive version (HEAB) was later relocated to the center of the grenades in order to optimize the fragmentation shape. For cost reasons, the HEDP version was equipped with a COTS head igniter, which led to the characteristic tip. The later 25 × 40 mm grenades from ATK, however, are equipped with a rear fuse and are fired by the HK XM25.

technology

construction

The control electronics of the high-explosive version (HEAB) sat in the middle of the grenade and took up about 33% of the volume of the grenade. The system consisted of the mechanical safety and arming device and the microelectronics, both developed by Kaman Dayran. In contrast to the 20 mm grenades, the fuse was not designed as a microsystem, but as a macro system with a thickness of 7.6 mm. The mechanism was designed as a kind of spindle escapement, which was released when fired. For cost reasons it was made entirely of plastic. Despite this choice of material, the system was able to withstand 100,000 revolutions per minute and 100,000 g and was qualified according to MIL-STD-1316. The subsequent electronics module consisted of three printed circuit boards , which were built into the grenade stacked lengthwise and connected to one another. It could be programmed by the fire control system via contact strips on the outer wall of the projectile. Here, one was two-way communication possible to increase the reliability. The grenades could be reprogrammed as often as required if the pivoting laser of the fire control system switched to another target. The module also contained the time fuse, which triggered the air explosion of the ammunition over the target by a countdown . To improve precision, the muzzle velocity of the grenade was measured by the grenade itself, presumably via the contact strips. It had its own energy supply via batteries. Normally, however, the contact with the tapes charged a capacitor , which supplied the electronics with energy. A bleeder resistor was also built in to make the grenade incapable of detonation 90 to 210 seconds after it was fired. The contact fuse was independent of the electronics and ignited the grenade on impact when it left the security area (approx. 50 m).

Due to the larger surface area, the front and rear warheads of the 25 mm XM1019 HEAB could be simpler than those of the 20 mm XM1018: Instead of using hot isostatic pressing (HIP), steel plates were first pre-notched in a two-stage process in order to create the predetermined breaking points when splintering, and then pressed into the thimble shape. The version XM1049 HEDP first used a rear fuse with a shaped charge made of copper, later it was changed to a pointed head fuse , already on the market , and a shaped charge made of molybdenum . Both variants used LX-14 as an explosive. This consists of 95.5% HMX , the remaining 4.5% are thermoplastic polyurethanes and binders. The XM1051 stun grenade took over the center fuse of the XM1019 HEAB. All variants used the same aluminum cases, the same propellant charge and the same percussion caps . The ammunition's recoil impulse corresponded to a 12.7 × 99 mm NATO bullet .

variants

For the General Dynamics XM307 and the Barrett XM109 , a total of six projectile variants were planned, all of which were almost ready for series production. In contrast to the 20mm family , no gas grenades were developed. ATK later offered a chain gun called the LW25, which could fire this ammunition. The grenades were given a color scheme so that they could be identified quickly.

  • XM1019 High Explosive Air Burst (HEAB): A programmable, air- igniting high- explosive grenade. The color scheme is yellow.
  • XM1047 Blank (Exercise Ammunition): Exercise ammunition . The color scheme is gold.
  • XM1049 High Explosive Dual Purpose (HEDP): A multi-purpose grenade with a shaped charge, fragmentation jacket and contact ignition. Penetrates 51 mm RHA . The color scheme was red, later recognizable at the top.
  • XM1050 Training Practice (TP): A training grenade without a warhead. The color scheme is blue.
  • XM1051 Target Practice-Spotter (TP-S): A programmable, air -igniting stun grenade. The color scheme is blue with a red nose.
  • High-Explosive Incendiary (HEI): Explosive incendiary ammunition , structure like XM1049 HEDP but without a shaped charge.

Web links

Individual evidence

  1. ↑ globalsecurity: XM307 Advanced Crew Served Weapon
  2. ↑ a b c globalsecurity: Advanced Crew Served Weapon (ACSW)
  3. ^ A b c John H. Edwards: Force Effectiveness Leap with OCSW . Ed .: Department of Defense. 2000.
  4. ↑ a b c globalsecurity: XM109 Anti-Materiel Payload Rifle
  5. ↑ BARRETT: XM109 BRIEFING UPDATE , May 11, 2004 ( memento of July 19, 2013 in the Internet Archive )
  6. ↑ World of Guns: XM25 grenade launcher / air bursting assault weapon (USA)
  7. ↑ Janes: 25 × 59 B XM307 / LW25 grenades
  8. ↑ a b ATK: Fuzing Innovations for Air Burst Munitions: A 25mm Case Study , April 2005 (PDF; 700 kB)
  9. ↑ a b XM307 Program Reliability Growth, Ammunition Development and Advanced Technology Demonstration Tests , 2003 Small Arms Symposium & Exhibition National Defense Industrial Association May 13, 2003 ( Memento of December 28, 2016 in the Internet Archive )
  10. ↑ ATK: Fuzing Innovations for Air Burst Munitions: A 25mm Case Study , April 2005 (PDF; 700 kB)
  11. ↑ KAMAN DAYRON, Inc: Miniature Verge Escapement Safety and Arming Device , 2004 ( Memento from December 26, 2016 in the Internet Archive ) (PDF; 290 kB)
  12. ↑ a b General Dynamics Ordnance & Tactical Systems: Advanced Crew Served Weapon (ACSW) -XM307; Ammunition Crew Safety & Precision Air-Burst , April 2005 (PDF; 1.4 MB)
  13. ↑ ATK: Development of LW25 Family of Ammunition , 2008 ( Memento from March 4, 2016 in the Internet Archive ) (PDF; 191 kB)