|JANE'S DEFENCE WEEKLY - OCTOBER 05, 2005
INFANTRY WEAPONS - SMALL ARMS AND THE SOLDIER
*The US Army's intention to replace its 5.56 mm weapons presents a rare opportunity for change in NATO
*Other armies are increasingly adopting rifles in bullpup configuration
*Whichever cartridge is chosen by the US will be in service for decades to come
The US Army's intention to replace its entire family of 5.56 mm weapons will have repercussions for all future NATO small-arms calibres. Anthony Williams reports
For the past quarter of a century, NATO has relied upon two different rifle/machine gun cartridges: the 7.62 x 51 mm and the 5.56 x 45 mm. The US Army's present intention to replace its entire family of 5.56 mm weapons with new equipment provides a rare opportunity to reconsider that choice.
Evidence from recent conflicts questions the effectiveness of the 5.56 mm round and suggests that the opportunity for a review should not be ignored. What is clear is that the decisions taken by the US over the next few months will determine NATO small-arms calibres for the foreseeable future.
New small arms for the 21st century
The US Army uses two distinct families of weapons in 5.56 x 45 mm calibre: the M16 rifle and the derivative M4 carbine form one group, the M249 Squad Automatic Weapon the other. The M249, a licence-produced and much-modified version of the highly successful Belgian FN Herstal Minimi light machine gun, was purchased in the 1980s and the guns are now wearing out and need replacing. The US Army has also decided to replace the M16/M4 family with a different design, for more complex reasons.
The constant search for a more effective infantry weapon led in the 1990s to the concept of small-calibre high-explosive fragmentation grenade shells designed to burst over the heads of their targets, thereby permitting the attack of troops in defilade, ie hiding behind cover. Studies indicated a dramatic improvement in the effectiveness of small-arms fire. Ensuring that the shells explode at precisely the correct point involves some sophisticated technology. This includes a laser rangefinder coupled to a ballistic computer linked to the sights to ensure that the user aims the weapon accurately. The computer also provides data to electronically set the shell's time fuze as it is fired so that it detonates after travelling the correct distance.
Two different weapon projects were initiated to use the new high-explosive airburst technology. One was the Objective Crew Served Weapon, now known as the Advanced Crew Served Weapon and designated XM307; this is a machine gun in 25 mm calibre. The other was the Objective Individual Combat Weapon, also known as the Selective Assault Battle Rifle and designated XM29. The XM29 was intended to be a shoulder-fired, semi-automatic grenade launcher in 20 mm calibre and to incorporate a compact, lightweight 5.56 mm rifle as a back-up weapon. The development team, led by Alliant Techsystems Corp, included Heckler & Koch (H&K) of Germany, which won the contest to supply the 20 mm and 5.56 mm gun mechanisms.
The XM29 ran into difficulties when it proved impossible to reduce theweight any lower than 18 lbs (8.2 kg), the target being 15 lbs. A decision was therefore taken to continue separate development of the rifle and grenade launcher elements, while at the same time increasing the calibre of the grenades to 25 mm to improve their effectiveness against troops in body armour. Development of the grenade launcher is proceeding as the XM25, while the rifle element was redesignated XM8.
The XM8 design is based on H&K's successful G36 rifle, with various modifications required by the US Army. It is clearly a much lower-risk project than the grenade launcher and is already close to maturity; plans to carry out large-scale troop trials have been drawn up. The XM8 is of modular construction and barrels of different lengths and weights can be interchanged to meet tactical needs, producing carbine, compact carbine, sharpshooter, and - with a long heavy barrel, a bipod and a large-capacity magazine - an automatic rifle.
However, it was decided to include a belt-fed light machine gun variant in the programme, instead of the automatic rifle, to replace the M249. In view of this change another competition was announced for the new family of weapons rather than automatically selecting the XM8. A request for proposals was published in May 2005 with a timescale of 180 days in which to respond with written submissions along with four examples of each variant for testing. In July this was superseded by a further decision to suspend the competition in order to consider the needs of all of the services, not just the army.
To complicate matters further, a different competition has been running in parallel for a new rifle for US Special Operations Command (SOCOM) forces under the designation Special Operations Forces Combat Assaul