SG20 ChemRail

TST SG20 ChemRail dual-stage linear motor rifle

Zapadoslavia

various PMCs

### Variants

StockLMG (extended heavy-duty barrel, high-capacity drum magazine, high-output capacitors, improved cooling system, bipod)

Marksman (extended high-precision barrel, high-output capacitors, bipod, advanced scope, fire-control computer)

Grenadier (standard-length heavy duty barrel, 25 mm semi-automatic smart grenade launcher)

"ChemLite" carbine/SMG (significantly shortened frame, short barrel, extended magazine)

## Specifications

### Barrel Length

760 mm (standard)870 mm (extended)

480 mm (short)

### Cartridge

8.7x52mm FSDRAS (fin-stabilized discarding rail accelerator sabot)

### Feed System

mechanically-assisted electrically-actuated

### Sights

integrated 4x20 binocular smart scope

TST SG20 ChemRail dual-stage linear motor rifle (DSLMR) is a powerful hybrid-propulsion firearm combining the reliability of traditional chemical propellants with the brute force of electromagnetic linear accelerators, or railguns. Commonly seen in the hands of various elite soldiers and mercenaries, the SG20 is most notable for it's widespread use by the Baltic Union military, being the service weapon of its elite Tier One forces and, to a limited degree, Tier Two regular troops.

## Background

One of the largest Old Nations military contractors, Trautmann-Schneider Tacticals (TST) is known mainly for its large-caliber vehicle-mounted railguns. The SG20 is the most successful product of the company's attempts to enter small arms market.

Initially conceived as a replacement for the SG90 assault rifle as the service weapon of the Old Nations armed forces, the new weapon was designated as *Sturmgewehr-20,* or SG20 for short. Although it wasn't the first rifle to use hybrid chemical-electromagnetic propulsion, earlier examples including Mecharussian 6P8 series and the Frenkish M88 HBR, the SG90 would incorporate many advanced features and technologies, such as integrated energy reclamation system in the recoil dampers and independently-powered magnetic rails made possible by recent advances in power storage technologies. The result was a highly-sophisticated and extremely powerful gun.

Despite the considerable investment in its development, SG20 failed to secure any major military contracts, however. It was a rather heavy and cumbersome weapon for its intended role, with an uncomfortably-powerful recoil for the average user, making it difficult to use to full effect without wearing a combat exoskeleton. Although TST constructors had made every effort to keep the design relatively simple and very robust, it was still a complex piece that only highly-skilled operators could service and maintain safely. As such, the SG20 was ill-suited for its intended role as a standard-issue service rifle. Furthermore, the cost of one unit was equivalent to eight SG90's, which the ON military was already in no hurry to replace.

While the SG20 project failed to meet its ambitious original goals, the ON government purchased enough SG20's for special forces use to keep the project from being canned. The weapon was consequently rebranded and marketed as ChemRail, as the TST marketing department felt the new product needed a catchy brand name that would stand out amongst other firearms already produced by TST's main rivals, Mauser and Krupp-Rheinmetall. ChemRail was consequently chosen as a reference to the weapon's hybrid propulsion system, and coincidentally, a popular pre-War conspiracy theory.

The weapon consequently found some success abroad, being purchased in small numbers by foreign special forces, security and PMCs. It is popular with well-funded mercenary groups who are bound to have at least a few in their armories for use in especially tough missions, and also as a show of force. The single largest consumer of the SG20 is the Baltic Union that has made it the standard service weapon for its elite Tier One commandos. Arguably the best-trained special forces in the Solar system, Tier Ones have the necessary skill to use the SG20 to its full potential. SG20's have also seen a limited proliferation within the Union's Tier Two regular forces, assigned to the most experienced troops, and has hence become something of a mark of status. SG20's intended for Baltic market are different from baseline models, manufactured to their specifications that require high modularity and customizability, and extra sturdiness.

## Overview

A recent and highly advanced design, the ChemRail currently represents the final word in high-powered infantry arms. Accelerating tungsten-carbide flechettes encased in aluminum sabots at speeds in excess of Mach 16, ChemRail has effectively made most conventional cover and any practical amounts of body armor obsolete.

Every flechette has its base encased in a conductive aluminum sabot, and has a small "kicker" charge of Nitramide 50 caseless propellant attached to the base of the flechette. This first explosive stage is necessary to give the projectile the initial impulse that would blast it clear of the barrel even if the second electromagnetic acceleration stage failed completely. In early prototypes, this was accomplished by a blast of compressed gas, but the impracticality and hazard of carrying around compressed gas cilinders on the battlefield led designers to adopt a compact, reliable and time-tested solution of using a low-explosive propellant, even it it was considerably more taxing on the cooling system. The first explosive stage is also necessary to prevent potentially-catastrophic jams. When the rail capacitors discharge, the intense magnetic fields that drive the projectile forward also cause induction heating within the conductive sabot, leading it to heat tremendously. This happens so rapidly that unless the projectile is already moving down the barrel at considerable speed, the aluminum sabot may partially melt and fuse to the rails before the electromagnetic impulse can launch it clear of the barrel, leading to a catastrophic and potentially deadly failure of the weapon.

Once the flechette is set into motion, the weapon's capacitors discharges into the four independently-powered rails that guide the projectile, accelerating it to hypersonic velocities. A liquid-helium cooling system that keeps the rails chilled greatly improves the effectiveness of the electromagnetic stage. The combustion products of the first-stage propellant charge are vented through ports in the sides of the barrel, serving no further function in accelerating the projectile. Less than 5% of the ChemRail flechette's kinetic energy is generated by the first-stage propellant, although it is still enough to propel the flechette clear of the barrel at lethal velocity even in the event of a complete failure of the linear accelerator stage.

Because of the extreme muzzle velocities, the SG20 packs a hefty recoil. Advanced recoil dampers in the stock reduce it to more manageable levels, but the operator must still be very stockily-built or wear a powered exoskeleton to control the weapon effectively for anything more than short bursts. The recoil dampers also integrate an energy reclamation system that generates electricity from the absorbed recoil and re-loads it into the weapon's power cell, allowing as much as a dozen extra shots to be taken before a recharge is needed.

The extreme muzzle velocity also means the SG20 has a very flat trajectory and minimal projectile travel time, making it superbly accurate especially in the stabilized extended-barrel Marksman configuration. The effective range of the weapon is limited to about 2500 - 3200 meters, depending on flechette material - at such extreme velocities, air friction rapidly heats the flechette so much that it cannot retain its integrity above a certain range, simply vaporizing or disintegrating in burst of sparks.

The standard armor-piercing flechettes are made of a tungsten carbide - cobalt alloy, and are effective against all types of unarmored and lightly-armored targets. At close ranges, the SG20 is capable of defeating up to 50 millimeters of modern composite armor, with enhanced-penetration flechettes made from depleted uranium able to punch through as much as 70 millimeters of armor. Against soft targets, the sheer amount of kinetic energy dumped by a penetrating flechette is often enough to cause the surrounding tissue to expand explosively, to an extremely gruesome and deadly effect - in fact so much so that some groups have decried the ChemRail to be a barbaric and inhumane weapon and called for its ban. TST likewise manufactures reduced-penetration flechettes built from sintered metal powder, designed to disintegrate on impact with a hard surface, for uses where overpenetration is a concern.

Operators in the Baltic Union have come up with their own custom-made flechettes, such as expanding hollow-point flechettes made of soft untempered iron. Found to be extremely devastating against unarmored targets, these "hot shots" are the subject of much controversy especially with their recent use in warfare against the Mechanocracy of Russia. Enhanced-penetration flechettes of depleted uranium are also produced and used in small numbers, though their increased mass is more taxing on the weapon's barrel and power systems, regular use significantly shortening maintenance life.

Each SG20 comes with an integrated iOPS-204 digital 4x20 smart-scope. Using an array of optical and laser-based instruments, the smart-scope's processor automaticaly calculates the optimum aiming point for the designated target (marked with a push of a button on the side of the weapon), taking into account factors like wind speed, gravity, Coriolis force, air humidity and target's own movements. This allows even a user with minimum training to land shots with high precision at a long range.

The SG20 ChemRail is a modular weapon, designed to be easily converted from stock version into one of its commercial variants. Conversion kits are also manufactured and supplied by TST, allowing operators to convert their standard ChemRails into LMG, Marksman or Grenadier variants simply by swapping the barrel and mounting the rest of the necessary add-ons on Picatinny rails or the appropriate component slots. A trained operator can convert the weapon in under 40 seconds.

A small carbine/SMG-sized version, the MP20, is also produced by TST and marketed as ChemLite. Although considered a variant of the original ChemRail, ChemLite's technical differences go beyond the mutually-compatible modular parts, effectively making it a different weapon, if still highly-similar and nominally part of the same series. Being more lightweight and manageable, the ChemLite can be comfortably operated without a powered exoskeleton while still punching well above its weight, making it a popular choice among Baltic Union's Tier One support troops (pilots, medics, drivers, etc.), and private security companies that routinely operate in settings where full-sized ChemRails would be impractical and/or illegal.

While no doubt a versatile and very formidable weapon, the SG20 ChemRail is a rather expensive piece of engineering, the price of just one exceeding that of a whole squad's inventory of more conventional rifles, averaging at around 48 000 Frenkish dollars. For this reason, it is rarely seen outside the armories of special forces and elite PMCs which can afford it.

## Trivia

The ChemRail is a rather obvious reference to the film *Elysium*, where an almost identical weapon is used to significant effect. However, it is only seen in action during a single scene, no further elaboration beign given on its origins or capabilities beyond quite obviously being a very powerful electromagnetically-powered rifle.