The central idea of the program was to develop a rifle that enabled the attacking of targets behind cover by using airburst munitions. The munitions were to be much smaller than pre-existing grenades and grenade launchers, but large enough to be effective. The idea was refined into a combination of a short assault rifle and semi-automatic, low-velocity cannon firing air-bursting munitions. The OICW aimed to use advances in computer technology in a weapon that fired grenades automatically pre-set to explode above or beside targets hidden from view. Fragmentation from the exploding grenades could hit the target when normal rifle fire could not. The technology would represent the first smart weapons fielded by U.S. soldiers, with semi-guided munitions that hit targets at angles or behind targets ordinary weapons could not (such as with a guided missile), which would significantly increase accuracy.
The winners of the first competition for the project during the 1990s were ATK and firearms manufacturer Heckler & Koch with the XM29 OICW. They went on to build numerous prototypes of the rifle for the United States military in the late 1990s. These projects centered on using a programmable 20 mm airburst munition-firing rifle by itself or with other projectile-based weapons attached. The 20 mm launcher was analyzed in various configurations, including a launcher by itself, with a 5.56 mm weapon (based on the HK G36), or with a MP7 PDW.
By the early 2000s, the weapon had settled on a design and was classified as the XM29. The XM29 was based on the HK CAW (Close Assault Weapon) (Cal. 18.5×76mm or 12 Gauge non-conventional). However, the weapon had serious problems: it did not meet weight or cost targets, and the 20 mm XM1019 High Explosive Air Bursting (HEAB) did not seem to be lethal enough in testing. To compound matters, the kinetic-energy component had to be light and short in length. As a result, the 5.56×45mm NATO barrel had a length of only 250 mm (9.8 inches), which is too short to generate enough muzzle velocity to be effective. It was also too heavy and too large to be operated effectively by a soldier. The weapon was nearly 18 pounds, which was already 3 pounds over the program 15 pound specifications. In comparison, the M4 carbine is just under 7.5 pounds loaded, while the M16 with a grenade launcher is approximately 12.5 pounds fully loaded with an M203 grenade launcher. The excessive size combined with the relatively poor firepower shelved the operation and broke off in to two weapons, neither that have gained a wide degree of success, although the M25 is still in used by the Army.
25mm Air Bursting Grenade
While the OICW project was canceled, the air bursting munitions program would later go on to continue. The weapons were split in to two distinct weapons, which significantly reduced the weight and improved the functionality of both, neither being significantly hindered by the other, greatly improving the XM25's capabilities. The weapon itself was upgraded to use a larger, 25mm grenade, which the weapon could now afford as it was made to be much larger. Holding up to 4 rounds and firing them in quick semiautomatic action, the weapon was quickly knicknamed "The Punisher" by soldiers due to it's destructive power and in general it's particular ability to take down snipers or marksmen at long ranges who frequently retreated behind cover. As the grenades were programmed to blow up in mid-air, they could be fired at an enemy soldier and even if the round missed, say was 3 feet from the target, it's area of effect would allow it to still take down the target. Furthermore, the weapon could blow up in a more ideal place, rather than only with an impact detonator that required the round to be detonated against a solid object; thus if no object could be used to detonate the round in an ideal place, 25mm grenades could be used to have them detonate perfectly in the right spot. Within seconds, a well placed grenade could be fired in to a building and take out the target even if the user couldn't see them; accuracy was significantly improved over standard rifles as even misses could guarantee success. Furthermore, with a range of approximately 500-700 meters for the air bursting mechanism and 1000 meters total, it's range was far greater than the 150 and 400 meters respectively of the 40mm grenades. Due to the airbursting nature, the grenades were considered to possess around 300% greater effectiveness than the 40mm grenades, and on top of this were capable of penetrating the same type of armor and producing roughly similar blast radius's. [1][2]
The weapon does possess considerable drawbacks however. First, it's approximately 14 pounds, which is quite heavy, even for a primary combat weapon (being much heavier than the 6.5 pound M4 carbine). The weapon only holds 4 rounds and comparatively each round is much heavier than standard 5.56mm or even 7.62mm ammunition, which limits the amount of ammunition which can be carried further. While the 40mm grenade is nearly half a pound and the 25mm grenades are much lighter, they still nonetheless are substantially heavier than bullets which are just 1/36th of a pound. Further, the weapon possess no secondary defensive weapons; as a result of the explosives which can only be used at range from the user (or risk injuring himself) and the small magazine capacity, the weapon performs poorly at close range for self defense purposes. As a niche weapon, it can only perform it's specific duty, which means that a soldier's only use on the battlefield is as a specific grenadier. Due to the weapon's excessive size and weight, it's a difficult weapon to carry in to combat, being nearly 14-15 pounds, and thus on top of existing equipment (which can be well over 75 pounds for standard combat gear), can become too impractical to use in certain situations. As a platoon level firearm it functions fine, especially in weapon's companies, but at the squad level it can become a hindrance to the mobility or function of a squad.
Objective Individual Combat Weapon
While the program was eventually canceled, there are ways to potentially rectify many of these problems. Almost the entire weapon's problem was the weight and resulting lack of firepower for it's size. The barrel of the secondary assault rifle or, kinetic energy weapon was just about 10 inches, which significantly hindered the velocity of the round, especially compared to full sized rifles. The weapon was 34 inches long, roughly the length of a fully extended M4 carbine, yet had a substantially shorter barrel. The shorter barrel made the weapon substantially weaker and gave it a much shorter range, with only approximately 1200 joules compared to 1800 joules. As the 5.56mm was a velocity dependent cartridge, which needs a higher velocity to reliably tumble or fragment, this complicated issues further. The grenade launcher aspect of the weapon was also extremely heavy, with the XM25 on it's own weighing at least 12 pounds. Finally, the thermal scope adds a minimum of approximately 2 pounds, which is necessary for the laser-range designator that programs the 25mm rounds to detonate at a long range. Under the best of conditions, the weapon only achieved an 18 pound weight.
Interestingly enough, underbarrel grenade launchers that are relatively lightweight have existed for many years. The M203, which is just 3.3 pounds, or 3.8 pounds loaded, fits under the rifle and due to it's firing system of a high-to-low pressure, has extremely light recoil, despite it's small size. While the weapon can be fired as a stand alone weapon, when combined with a rifle the stock, pistol grips and general ergonomics of the rifle increase the ability of the user to manage the recoil. Further, the increased weight decreases the recoil, as it's absorbed by the heavier weapon. Rather than make the grenade launcher heavier, such as with the M79, to make the recoil easier to absorb, instead it relies on the weight of the rifle, which reduces the weight of the pair. The grenade launcher's recoil is absorbed by a 12.5 pound combined rifle weight, instead of just a 3.3 pound launcher. A 40mm grenade can penetrate 2 inches of steel, compared to about half an inch for a .50 caliber round, and take out a car engine or group of soldiers despite it's small size and weight, giving an incredible addition of firepower to any squad with little to no drawbacks. If the grenade launcher is added to the assault rifle, rather than an assault rifle added to the grenade launcher, than very little if any utility is lost for the assault rifle, which maintains the same barrel length and overall lightweight and compact size for the extra firepower. However, the grenade launcher's ability does diminish; being shorter, it has a shorter overall barrel length, necessitating a much lower velocity round, which provides less accuracy and a shorter range. It also is not semiautomatic, which means it can only fire one round at a time, significantly hampering it's firepower and versatility, in particular it's ability to fire multiple rounds quickly (such as door breaching rounds followed by explosive or flashbang rounds).
The 3GL, in many ways, resolves most of these firing issues. With a radially stacked, linearly fired round, operating similar to a roman candle, with multiple rounds fired after each other stored in the barrel (which is also the mgazine), the weapon can fire multiple rounds fairly quickly. Using caseless rounds that are electrically ignited it's incredibly simple in operation, has little chance of a cook-off and is very reliable. Furthermore, the rounds are lighter weight, and the reduced complexity of the firearm allows it to be extremely small and low profile. If fitted with 25mm grenades, it can more than easily fullfill the XM25 requirements, although it holds one less round. The grenade launcher comes in at approximately 5.5 pounds; however, other grenade launcher have shown considerable promise in reducing the weight. Grenade launchers such as the polymer reinforced XL200 are around 40% lighter weight, or can reduce a 3.3 pound grenade launcher to approximately 2 pounds. This means that, if the same high strength materials and ribbed designs were used, the grenade launcher could become even smaller. At 3.3 pounds, this grenade launcher would be almost identical in terms of weight to an M203, and would be much lighter. The combined weight of a fully loaded grenade launcher and M16 would be almost identical in weight; not only would it exceed the weight requirements of the 15 pound OICW project, but it would actually meet the weight requirements of a standard M16 combined with a grenade launcher. Further advances in range and accuracy while maintaining the same firepower of the 40mm grenade would be retained in the 25mm grenade launcher, as well. If the grenade launcher was designed to be on top of the rifle, instead of underneath it, it would also allow the barrel length to be maintained instead of shortened for shorter rifles (significantly), allowing it to possess the same long barrel that allows for greater firepower and range.
This grenade launcher not only maintains the same advantages, but also can serve as an attachment to a rifle, meaning that switching to using the grenade launcher and standard weapon variant are much easier. The weapon has a longer barrel on both mechanisms and is generally able to use fullsized options of both. It's reduced size and complexity makes it lower profile and lighter weight, allowing it to far exceed the requirements by the program, while still maintaining the high firepower. The only remaining difficulty in the design is the thermal scope and laser range finder; needing both for airbursting munitions, one would need to replace the trigger and handguard of the rifle to allow it to more ergonomically program the weapon and in addition allow the trigger to fire either round. Relatively easy to do simply by adding a new accessory, wires can simply run to either device, which make the weapon easier to fire and thus, reduce the need for added parts. Non-airbursting grenades could be quite easily used out to 1000 yards as well if thermal vision scopes, the most expensive feature of the gun, are not utilized. The weapon now afford to hold 3 rounds of air-bursting 25mm grenades, even on an incredibly short weapon, with the same overall retained barrel length and more than exceeding the weight requirements of the OICW program.
