6.2mm x 39mm SAW Aluminum
The 6.2mm SAW cartridge is based on the 7.62mm x 39mm case, with an aluminum case instead of steel or brass, and necked down to have a 6.2mm, .243 caliber bullet. The bullet is designed to have a very high ballistic coefficient and sectional density, with a BC of .617 and that is 110 grains (7.15 grams). The bullet is slightly smaller than the 7.62mm x 39mm bullet at 123 grains (8 grams), but has more energy, with 2600 joules from the same 16 inch barrel, in comparison to 2000-2200 joules for the 7.62mm x 39mm. The cartridge is designed to use AA2200 powder, like used in the .25-45 sharp, which is more powerful for the same volume of powder, or 35 H20 grains (2.2 grams). The powder also utilizes a hexagon binder similar to a caseless cartridge, which reduces it's heat sensitivity and makes the weapon unlikely to have a cook-off. Due to the more powerful powder, the firearm is more powerful than 7.62mm x 39mm for the same amount of power, and has slightly less recoil for the same level of power, with greater power from longer barrels. Due to the longer bullet, it seats deeper in the case, and takes up some of the The majority of 7.62mm x 39mm firearms can easily be converted to the 6.2mm SAW cartridge merely by swapping out the barrel, using the same magazines and bolt, however typically the spring and bolt are replaced. The higher pressures of the cartridge do require more powerful material construction for reliable or long term use, but the same design of the 7.62mm x 39mm firearms can be used for the 6.2mm SAW cartridge. A typical 7.62mm x 39mm cartridge weights 16.3 grams, with 2.2 grams of powder, 8 grams for the bullet, and approximately 6.1 grams for the case. The 6.2mm saw is a mere 11.35 grams, with 2.2 grams of powder, 2 grams for the case, and 7.15 grams for the bullet. This is 43% lighter than the 7.62mm x 39mm, around the same weight as the 5.56mm x 45mm NATO at 12.5 grams, and less than half the weight of the 25.5 gram 7.62mm x 51mm NATO cartridge.
Despite the reduced power in regards to full sized cartridges like the 7.62mm NATO, the higher aerodynamics gives it longer range than the 7.62mm NATO, and the cartridge still possess more power than most intermediate cartridges like the 7.62mm x 39mm or 5.56mm x 45mm NATO. From a 16 inch barrel, the round generates approximately 2600 joules, which is 30% greater than the 7.62mm x 39mm, and 45% greater than the 5.56mm from a 20 inch barrel. The round possess significantly higher power, and from a 20 inch barrel is roughly on par with the .280 British. This allows it to be more readily used in carbine length weapons, although it can produce greater muzzle flush. From a 16 inch barrel, at 1525 yards, the bullet is still super sonic (above 340 m/s), giving it a very long effective range; the round also still has more energy than the 5.56mm at the muzzle at 350 yards, and more energy than a .357 magnum at 800 yards. The round due to it's high sectional density retains good armor penetration even at long range, and with hardened armor penetrating tips is better at penetrating armor than the 5.56mm.
The round produces between 2350 joules and 2950 joules between a 12 and 24 inch barrel, using fast burning propellant based on the AA2200 powder of the .25-45 Sharps. The cartridge was designed for a 16 inch barrel, equivalent to that of an Ak-47, to be used out of similar 7.62mm x 39mm firearms, and produces 2600 joules with a velocity of 850 m/s, using a 7.15 gram bullet. With 1 MOA of accuracy, it is very similar to the 6.5mm Grendel in performance, which it is based on (using the same case, which is also the same case as the .220 Russian and 7.62mm x 39mm), but is slightly more aerodynamic and slightly lighter weight, using slightly more powerful gunpowder. It is somewhat less accurate than the grendel, but uses more powerful gunpowder which burns faster in shorter barrels. Originally designed for the OTS-Groza 6mm, it can be used in a wide variety of firearms, but produces sniper rifle level accuracy and range from a low recoil, fully automatic, 25 inch long weapon. In
comparison to the 7.62mm NATO or 7.62mm x 54mmR, the round maintains it's super sonic velocity at longer ranges, and has more energy by 350 yards, despite a lower starting muzzle velocity. The bullet is 6.2mm in diameter, but is compressed to nearly 6mm in the barrel. The 6.2mm figure is primarily used to delineate it's difference from the original 6mm SAW, even though the rounds use the same sized bullet (like the .38 special and .357 magnum). The bullet uses the same 6mm diameter bullets.
The aluminum case is much lighter, allowing more rounds to be carried on the person and in each magazine with greater reliability. However, aluminum is prone to galling and causing fires, and does not prevent heat transfer to the barrel of the weapon as well as brass, resulting in higher chamber and barrel temperatures, causing the weapon to overheat faster. To remedy this, the case is coated in a thin layer of silicon dioxide, a silicon lubricant, and a thing outer layer of polymer, which not only reduces and prevent galling and friction, but helps serve as an insulator as well, keeping the rile cooler. The polymer coating is the same used in polymer cartridges, but less is used as to keep costs down below that of ordinary polymer cases. Around 30-40% more ammunition can be carried through the use of the lighter case, which is slightly thicker and stronger than a normal aluminum brass case. These can also be loaded in to the same firearms using the original 7.62mm x 39mm round, having roughly the same dimensions. The concept of the firearm is based on the
6mm SAW, and attempts to remedy many of the original problems. It is designed for use in both assault rifles and machine guns. While the kinetic energy is much higher than either the 5.56mm or 7.62mm x 39mm, the recoil is comparable, given the more efficient gunpowder and the various designs of the weapons, designed to help reduce the recoil, as well as a reduction in the mass of the case.
