Welcome to Gaia! ::

28mm Caseless

The 25 mm grenade is a type of explosive ordnance used in some modern grenade launchers; although in particular the grenade is essentially the same utilized in the XM25. 25 mm grenades are armed after launch, after traveling a safe distance. Many types explode on impact, but others are designed to explode in mid-air after traveling a certain distance—used to clear entrenched or barricaded positions. Examples of weapons designed to launch 25 mm grenades are the experimental XM25, the Barrett XM109 payload rifle, and the XM307 ACSW. The original use for this round was for the OCSW, now known as the XM307 ACSW. Later, a low velocity variant of the OCSW round was chosen for the XM25, which is derived from the XM29 OICW. There are two different versions of the 25mm grenade: the 25 x 40mm low-velocity round developed for the XM25, and the 25 x 59mm high-velocity round developed for the XM109 and XM307. The 28mm caseless cartridge is based on the 25mm x 39mm grenade used in the XM25 program, but is designed to be utilized with the caseless propellant and firing mechanism of the metal storm launcher. This makes each grenade shorter and capable of being fired even if linearly stacked, allowing it to be used in rapid fire grenade launchers like the 3GL, and allows each grenade to be lighter weight as they are caseless. This is similiar to the russian caseless grenades, however it's electrically ignited propellant makes the rounds safer and capable of being programmed to fire more precisely.

The cartridges are technically considered to be 28mm rounds despite the grenade itself being 25mm, due to them being embedded within the gunpowder of the cartridges, which are caseless. While this increases the width somewhat, it shortens it's overall size, making each cartridge approximately 2.9 inches long, instead of roughly 3.8 as their typical cased variants. The nomenclature does not actually denote the diameter of the barrel or the grenade which are 25mm. This also helps when linearly stacking the grenades such as in the 3GL grenade launcher, which shortens the overall length of the required firearms. Typically, these grenades are used in the XL-200 or 3GL grenade launcher designed to fire 25mm grenades instead of 40mm grenades. The smaller size of the weapons allows them to be used more easily as an accessory weapon to a primary rifle unlike the far larger XM25 which is 14 pounds, in comparison to just 1.3 pounds for the single shot variant and 3.5 to 5.5 pounds for the 3GL grenade launcher depending on it's variant. These firearms are also expected to be used with specialized caseless 12 gauge ammunition adapted for use in the 25mm grenade. The firearms will not actually fire 12 gauge ammunition and instead relies upon the same rounds being adapted with the newer propellant. They mimic the ballistics of 12 gauge specialty cartridges or improve upon them with the same or similiar rounds. This allows the weapon to use a number of specialty cartridges, notably door-breaching rounds and Frag-12 rounds which are far weaker but also lighter weight.

Metal Storm caseless cartridges
Metal Storm Limited is a research and development company based in Brisbane, Australia that specialized in electronically initiated superposed load weapons technology and owned the proprietary rights to the electronic ballistics technology invented by J. Mike O'Dwyer; Metal Storm represented both the name of the company and the technology. Caseless metal storm rounds are stacked on after the other and ignited by electricity, or can be ignited one round at a time. The rounds are essentially stacked on top of each other, and fire similarly to a roman candle, which simplifies the operating system, and allows for an overall incredibly short size and light weight. The company particularly focused on grenades, which are lower pressure and simpler in design, and benefit from holding 1-3 rounds and only need short barrels to operate. While the two main grenade launchers that fire the 28mm grenades are based off of the the 3GL, the grenade launcher is modified from the original 3GL, which due to the smaller size of the grenades makes the overall design much smaller (the barrel is roughly 40% smaller in terms of diameter, or about 1.6 times smaller in terms of area), and thus lighter weight, as well as it's heavy use of polymer. The grenade launcher utilizes much higher strength polymers in it's construction similiar to the XL-200 grenade launcher, which are more expensive, but increase the strength, and therefore decreases the required weight of the overall system. The 28mm version of the 3GL weighs approximately 3.5 pounds instead of 5.5 pounds for the original, and the XL-200 variant is 1.3 pounds instead of 3.5 pounds for the M320 or M230 grenade launcher.

Unlike ordinary cartridges which use the kinetic energy of a hammer falling, it instead depends on electricity to ignite the cartridges, which in turn makes the cartridges less susceptible to cook offs (rounds firing unintentionally due to heat, which is more common without the brass casing, which acts as a discardable heat sink), being ignited by an electronic primer. Like with the 3GL, 10's of thousands of rounds are capable of being ignited and cycled with the battery life of the weapon; however, the weapon utilizes the backwards motion generated by the gunpowder in each cartridge to create electricity, thus constantly keeping the weapon charged, with little need to recharge the batteries by other means when out in the field. Combining improved caseless powders from the G11 and LSAT series of firearms, the newer binder is significantly less sensitive to cook offs than traditional ammunition; while technically fually automatic, with an RPM of 210, the weapon is intended for semiautomatic use, only.

The original caseless ammunition from the G11 had a significant number of problems; the high rate of fire of the weapon itself and lack of cartridge cases made cooking-off a significant problem since the heat buildup in the G11 chamber was immense, due to the chamber having no provision for cooling, as with a reciprocating bolt system which allows hot air to leave the chamber when the bolt is retracted and the chamber is exposed to air. The vertically swivelling chamber furthermore made gas sealing at each end at such high pressures impractical, as opposed to a cross-sectional round-inside-round bolt-to-chamber fit with appropriate gas sealing. To solve this, Heckler and Koch formed a partnership with Dynamit Nobel who redesigned the cartridge to use a new High Ignition Temperature Propellant (HITP). The cook-off problem was reduced, by using a denatured HMX propellant with a special binder and coating for the ammunition that increased the spontaneous ignition temperature by another 100 °C above that of standard, nitrocellulose (180 °C) propellant. With modern changes in the propellant based on the metal storm and LSAT program, the gunpowder allows the cartridges to be fired without the risk of overheating or cookoffs, solving this particular issue, and it generally makes the weapon more reliable. The rounds are capable of being vertically stacked and superimposed to allow for multiple rounds to be fired in a row like a roman candle, however generally one round is fired at a time from a standard grenade launcher.

Shotgun

-FRAG-12
-Buckshot
-Door-breaching
-Rubber Bullet



FRAG-12 - While the 25mm grenade already possesses a variety of high explosive variations, the frag-12 offers a similiar grenade design, but much smaller, being a mere 32 grams vs. the 140 grams of the standard HE grenade. The smaller size is useful as it allows for explosives with varying degrees of power to be utilized, and for the user to carry a higher volume of ammunition with them, approximately 4-5 times as many grenades for the same weight. Combined with the fin-stabilization, the lighter weight allows for a higher velocity and range, providing an additional advantage for the lighter grenade. While the grenade is based on the Frag-12, it utilizes a slightly higher velocity, given the greater amount of propellant present with the 25mm grenade. Typically the velocity is between 400-500 m/s, which is similiar to the velocity of a 12 gauge shotgun. The shell uses a 50 mm (2.0 in) long metal body filled with 3.4 g (0.12 oz) of composition A5. Four folding fins spring out after leaving the muzzle. The shell arms at 3 metres (9.8 ft) and shell explodes on impact by MIL SPEC 1316 fuze. It has a maximum range of 200 metres (660 ft). The grenade lacks the effective range or armor penetration of the larger 25mm grenade, however it's area of effect being smaller helps to reduce civilian casualties and is more ideal for clearing out rooms. Similar to the Russian 40mm thermobaric grenades, it is designed to stun and injure individuals inside of a small room, and comes with a flashbang and secondary concussive effect, designed to stun as much as it is to injure or kill. This makes it less effective, with a lethal range of only 3 meters, and an injury range of 5 meters, but it is useful for clearing out bunkers or rooms and is relatively light-weight, allowing large amounts of ammunition to be carried.

Buckshot- Designed to mimic the 12 gauge shotgun, the shot-shells utilize roughly the equivalent shot of a 12 guage shotgun, which is 28-32 grams of shot, separate in to 8-9 pellets, at approximately 3.75 grams each, with each approximately 4.5mm in diameter, and traveling at 400 m/s. The round mimics the power of a 12 gauge shotgun, however it's designed to be fit to the 25mm grenade size, and thus is not actually a 12 guage shotgun round. Two variations exist, the original version designed to closely mimic the 12 guage shotgun, and the higher energy version, designed to exploit the larger case size of the 25mm grenade. It uses 12 pellets at a weight of approximately 45 grams, and accelerates them to 500 m/s, which provides slightly greater power than a typical 12 gauge shotgun shell, however it comes with substantial recoil and is generally only used in much larger variations of the gun/

Door-breaching- Perhaps the most commonly used shotgun variant of the 25mm cartridge, the door-breaching rounds are effectively the same as the 12 gauge shotgun, and utilize a clay-composite slug meant to destroy locks or other materials at close range but not significantly injure people behind the barrier. These will not cycle in a semiautomatic 25mm grenade launcher, and thus must be loaded manually one at a time. They are approximately 15 grams each, and are much smaller than typical 25mm grenades. They are based on the U.S. military clay shotgun door-breaching rounds, and have reduced lethality against humans targets, making them possible but rarely used as less-lethal rounds, given their higher potential for injury.

Rubber Bullet- The rubber bullet mimics the design of the 12 gauge shotgun, but is scaled up to fit the 25mm grenade size, and is much larger as a result. These are designed to be less-lethal cartridges, with the intent to stun or incapacitate the target without killing them, and have usefulness in riot control as well as in limited destruction of materials, such as occasionally being used for door-breaching. The cartridges are approximately 15 grams each, with a much smaller volume of propellant, due to the reduced power of the load. It utilizes 12 pellets at approximately 1 gram each, or one large bean-bag or rubber round at approximately 12 grams. The round is purposefully designed to be wide enough to disperse the energy over the individual, and covered in a disintegrating rubber foam, which helps to dissipate the energy of the much harder and denser rubber underneath. The rounds typically also contain colored paint and UV marking dye, as well as infrared marking dye, and this can be mixed with pepper spray or tear gas to disperse when the rounds strike the target. This aids in tracking the targets after they are struck, or further incapacitating them. The dye is easily visible with infrared or night vision goggles, and are heavily illuminated from the background when the marking dye is used, thus making them ideal for tracking the target with these types of scopes are used.