I present, after a lot of work and headache, the weapon I wished I'd had finnished for the Fictional Firearms contest: the Universal Modular Weapon Systems Modular Bullpup Rifle, 13
Caliber: can be converted to pretty much anything, but this one's in 6.8 Remmington SPC
Capacity: 30 rounds
Action: Can be converted to almost any gas system, this example uses a short stroke gas pistons
Fire modes: Semi, Auto, Safe
Notes: Full Comparability with many AR-type accessories, including: Pistol Grips, Rails, Trigger Guards, Magazines, Sights, Barrels, Flash hiders, Silencers, Buttpads, Selector Switches and Gas Systems
Aftermarket hardware: Magpul MOE grip, PMAG, MBUS sights, Milspec buttpad and trigger guard. FN Herstal Grenade Launcher, EOTech Holo Sight, Knight Arms AR Piston RIS.