The East PacificBoard

A 5.7mm PDW with a highly unique operation mechanism. There are several key components of the firearm to be looked into.

Operating mechanism and Feeding system
The most unique system is it's feeding system. It uses a rotating cylinder consisting of five chambers. However, these chambers are notably open walled. This means that the cartridges have to be triangular with rounded walls and corners. This allows the cartridges to be fed in from the sides, and removes the need of an assembly to push the cartridges in linearly and to be extracted. This, in theory, allows for a much higher rate of fire. As the cylinders rotate from the gas piston's travel backwards, it picks up a new cartridge, a spent one can be ejected from it just getting thrown out the side, and one can be fired with the cartridge pressing against the chamber and against the walls containing the revolving cylinders. This allows for, theoretically, a much higher rate of fire. The striker is charged by the rotating cylinder pushing back the pin and then tripping it when the cartridge is in position, almost like a reverse gatling system. Each chamber has its own firing pin that is reset by a small rail track that simply pulls it out enough to clear the next cartridge, and the striker itself is designed to roll of the rear of the firing pin, which itself is sturdy and blocky to improve reliability and simplicity of construction. The trigger stops it from firing by using two joined lug to catch the striker, and the cylinder stops when the gas piston stops oscillating. The gas cylinder is also made to be quite chunky to withstand the torque. To charge the mechanism, instead of pulling a handle back like on most guns, this instead has a geared ratchet parallel to the cylinder's rotation that the user simply pulls down on, which can be done by simply extending their thumbs upwards and indexing it, where as a spring automatically returns it back to it's position. Indexing the charging handle as such rotates the cylinder, bringing the striker back and rotating a new cartridge into the firing chamber. Safety is provided by simply stopping the lugs from moving out of the way with a simple blocking lug.

Internal magazine and reloading doctrines
The next unique system about this this a quad integral magazine using dual constant force springs. This magazine system also acts as the stock, and is reloaded by stripper clips, which is the next unique system to be talked about after this. The quad stack magazine uses a system similar to Magpul Magazine Patent No20100212653, with the notable difference of using two coiled up pieces of steel to act a constant force spring instead of using a misshaped coil spring. The cartridges are fed in by a spiral feed ramp in line with the revolving cylinder to be pushed in with the aid of two feeding ramps that spring the cartridge into place, which are toggled by two parallel sets of catches on the cylinder to allow for synchronization. Upon breaking the stock open, the magazine followers are depressed by a lever arm like a compressed air rifle does when it is broken. This is because the feed ramp and taper break with the stock, leaving the bulk, straight walled part of the stock magazine open. When firing from prone with it's simple sliding bipod, the barrel is tilted down and gun is broken upwards to allow for the clip too be inserted in. From a trench, foxhole, or behind a piece of cover that covers the majority of the body, the barrel is kept flat and the stock is broken down by slapping it, allowing the clip to be dropped in vertically. From firing while standing, crouched, or in the open in general, the shooter list to release the latch and break it upwards by pulling the pistol grip close to the chest and keeping the stock pressed against the shoulder, slipping in the clip and then closing it by applying torque to the pistol grip and returning the weapon to a shooting position. The charging handle must be toggled every time it is reloaded.

Ammunition and Ammunition Clips
The clip and ammunition have been referenced frequently and will thus be discussed now. The cartridges are of a unique, telescopic variety. Utilizing the polymers synthesized by the genetically modified yeast that secrete the spider-silk like protein strands that have been mineralized in a form of injection mold formed around the bullet itself, forming the triangular cartridges. These cartridges are rimless, as they need nothing for an extractor. The clips mentioned before, one would think, would have difficulty both in containing the cartridges and feeding into a quad stack magazine. This is where the beauty of the polymer cases come in. The clip is not a separate, stamped metal piece of either en bloc style, nor of the stripper clip style, per se. Rather, during the process of molding the cartridges, the triangular cases are molded together with a relatively thin plastic connecter, like one may snap parts of a model kit off of. So, with this in mind, the entirety of the clip is molded to fit within the quad stack magazine so that when the stock is closed and the follower puts pressure on the combined stack. This does not immediately break the stack apart, rather, the stack is flexible enough under the force that it roughly conforms to the walls of the magazine, with the pieces snapping under torque of the feed ramp and of the stacks converging. Upon the cartridge being fed, the bits of trailing plastic left are ejected out either when the case is spent and ejected or out of a small port on the opposing side meant to clear the larger obstructions. This lets the large, 120 round stripper clips, to be much more manageable than what otherwise may be expected. In addition, the triangular, telescopic ammunition allows for much more efficient packing density and also for smaller cartridges to be used.

Barrel and Bullets
The next notable aspect of the firearm is its barrel and bullets. Due to the fact that there are only three possible orientations for the cartridge to be in, suddenly, hexagonal rifling with a bullet already somewhat formed to that shape becomes much more practical. Using a progressive twist polygonal rifling, a heightened velocity and accuracy is achieved with a relatively compact barrel. In addition to this, because the amount of deformation the bullet has to undergo can be lessened by preforming it to roughly the same shape of the hexagonal rifling, the gas seal can be improved and the barrel wear lessened. By using a heavier barrel with a considerable array of cooling fins, the high rate of fire and extreme cyclic rate can be maintained over sustained periods of time to allow an infantryman equipped with such a rifle to maintain heavy suppressive fire over a longer duration of time to support his fellow infantrymen. The cyclic rate can be adjusted by increasing and decreasing the pressure of the return spring for minor adjustments, and major adjustments by adjusting the gas block itself, allowing from ranges of 900 to an impressive 1600. In order to make sure the return spring is properly adjusted for the gas block, turning the adjustment screw for the gas piston also adjusts the tension of the coil spring, where as adjusting the coil spring has no effect on the force of the gas piston although its limited to stay within the selected force's operational range. The barrel itself has hefty muzzle brake for its caliber, with the intended purpose of allowing the shooter to keep on target with more ease, with the high rate of fire itself making the weapon easy too control once you are on target, and especially when the bipod is deployed. For higher rates of fire, three round burst is recommended. For more suppressive fire, a lower rate of fire is recommended.

Misc. Features
The rifle is made to be easily filed strippable, with the operating cylinder made to be reversible for shooting with either hand as the dominant one. It has a built in bipod that can slide along a rail on the top and can be adjusted to practically any position on the gun, with detents above the center of mass and the front of the gun to act as a quick and easy locking location for when the shooter doesn't have much time nor need for the potential fine adjustments. The bipod is mounted just under a stop mounted Picatinny rail, meaning that the gun itself is slung just under the bipod. The bipod has basic telescopic legs held in place by a simple flat spring and detent combination. The Picatinny rail mentioned earlier is optional, depending on production circumstances. It uses a front blade style iron sight system to provide a comprehensive and clear look of the battlefield for rapid target acquisition, and a simple variable magnification scope may be added for 2.8x power up to 5x power.

General Overview
Starting from the muzzle to the stock, here is a general summarization of the Universal Purpose Assault Carbine. A muzzle break caps off a heavily finned barrel of a somewhat short and compact nature. A polymer heat shield obscures the bottom half, however it leaves enough open to reveal two separate adjustment screws for the gas piston system. The trigger guard is that of a very large variety for use with mittens, then front extending out some and the pistol grip connected with the stock to conceal the lever arm that depresses the magazine spring, giving the appearance similar to that of the FAMAS 2 and SL8. The receiver system is right above and slightly behind the pistol grip, with a metal construction for the top half. It is somewhat wider to house the revolving component, and there are dust covers mirrored on either side with two positions each, which will be adjusted based on which side is ejecting cartridges and which side is simply removing the plastic debris. The stock is of a thick, box like nature, tapering down to just under the receiver. There is a notable seam in the polymer between the main bulk and the tapering, as this is where the stock breaks open to reload.

OOC: Inspiration shenanigans
https://en.wikipedia.org/wiki/Polygonal_rifling
https://en.wikipedia.org/wiki/Dardick_tround
https://en.wikipedia.org/wiki/FN_P90
https://en.wikipedia.org/wiki/Fin_(extended_surface)
* https://en.wikipedia.org/wiki/Type_92_heavy_machine_gun
https://youtu.be/Fx8TcGrCOSI
* Spider beer shenanigans
https://en.wikipedia.org/wiki/Gatling_gun
**Anything that you can't determine to be inspired by the above is most definitely of my own derpiness, such as the way you have to reload it.

Our special thanks to Slagenseter forn for aid in this project.

Derived from the UPAC concept, the Heavy Assault Rotary Machinegun is a quad barreled belt fed weapon chambered in 5.7 mm polymer cased ammunition that is used in the UPAC, although the linkages are now made to be flexible to act as a belt. The design of the cylinder is nearly identical to the UPAC, although now each tround cylinder has their own barrel. To cope with the higher rate of fire expected, each chamber has its own hammer lifted by a cam to be dropped on the case primer. The cylinder assembly itself is allowed to freely spin in one direction thanks to a rachet system, and due to the lack of rearwards moving components a high rate of fire can be achieved. Each barrel has a gas block affixed, which expels some of the gas through a nozzle to impart spin on the HARM, with a ring of ventilation fins running perpendicular to the direction of expelled gass and providing something for the gasses to push off of, to provide extra thrust. The muzzles of each barrel have a halbeck-device like muzzle to further impart spin on the mechanism. To improve firing characteristics and hit probability, a second belt is fed into the system so both the top and bottom barrels will fire, applying more torque, decreasing horizontal push from just the top barrel firing, and increasing rate of fire greatly. With the above in min, the rate of fire is exceptionally high at around 4,100 rounds per minute once the barrels accelerate to peak velocities. A small electric motor akin to a civilian power drill is used to spin the barrels up to increase the initial fire rate to around 1,300 round per minute, where as it will exponentially accelerate until 4,100 rounds per minute is reached.