Frames

• Taser (Taser only)
• Hold-Out Pistol
• Compact Frame Pistol
• Full Frame Pistol
• Machine Pistol
• Submachine Gun
• Carbine
• Assault Rifle (Light Rifle only but I am toying with how to do Beowulf)
• Battle Rifle (Medium Rifle only but I am toying with how to do Beowulf)
• Sport Rifle
• Sniper Rifle
• Light Machine Gun (Light Rifle only)
• Medium Machine Gun (Medium Rifle only)
• Heavy Machine Gun (X Rifle only)
• Shotgun (Shotgun only)
• Assault Cannon (Assault Cannon only)

Ammunition Types

• Light Pistol (9mm and similar)
• Medium Pistol (5.7x29mm and similar light high speed rounds)
• Heavy Pistol (.45 and similar)
• X Pistol (.50 AE and similar)
• Light Rifle (6.5 Grendel and similar)
• Medium Rifle (7.62x51 NATO and similar)
• Heavy Rifle (.338 Lapua Magnum and similar)
• X Rifle (.50 BMG and similar)
  

For example: Medium Machine Guns, Battle Rifles, small caliber Sniper Rifles and mid caliber Sport Rifles all fire some round that is, for game purposes, functionally identical. Let's go with the 7.62x51mm NATO round because it's pretty common, and there's a civilian market version (.308 Winchester). All but the Sniper Rifle have barrels between 18" and 22" in length (the Sniper Rifle is 22" to 30" long). So why does every one of them have different penetration ratings? If the argument is that civilian weapons don't penetrate as well, tell that to the cop shot through his vest by a 30-06 rifle which arguably is even more powerful without getting to the next game-significant damage level.

So, the pistols are all designed to be held and fired with one hand (Weaver Stance not withstanding). I diferentiated then by a combination of barrel length and grip length. Several "Heavy Pistols" have a compact version listed (Walther Secura Kompakt) but have reduced ammunition and improved concealability. The approach seemed a bit ham-handed to me, so I diferentiated it by the side of the frame and then had a version of each by round.

Hold-Out pistols have barrels <4" (10cm) in length, usually have a single-stack magazine and a short magazine well. Small Frame and Full Frame pistols have the same barrel lengths (4" - 7"/10cm - 17cm), and share double-stacked magazine wells; What diferentiates them is the depth of the magazine well and the configuration under the barrel (most modern Full Frame pistols have a rail for a laser sight or small combat flashlight). Machine Pistols are diferentiated from Submachine Guns in that the MP has a pistol-length barrel and the SMG has a longer (7" - 10"/10cm - 17cm) barrel and most of the selected artwork has shown ammo feed through the grip for MPs and separate magazine well for the SMG. In other words, one's bigger.

Now, all rifles originate from the basic Sport (hunting) Rifle at some point. The Germans created the first "Sturm Gewehr" or Assault Rifle by combining a SMG-style automatic action with a cut-down rifle cartridge. After the war, what the Western allied powers developed were full rifle-caliber (7.62x51) versions of the German weapons. The Russians, in a case of parallel simultaneous evolution, had developed the AK-47 which used a cut-down rifle cartridge (7.62x39). The Battle Rifles were found to be 1) Heavy 2) Functionally uncontrolable in automatic fire and 3) Very difficult to keep supplied with enough ammunition if it had to be humped in by humans on their backs. The Americans eventually developed a specialized round (5.56x45 NATO) and evolved weapons around it which addressed all three issues. Ironically, the Soviets then followed suit and developed the AK-74 which fired a round (5.45x39) which was more similar to the newer, lighter American rounds. (Incidentally, that leaves the old AK-47 as midway between a Battle Rifle and a modern-style Assault Rifle by being both cut-down from rifle power, but firing a full caliber and notoriously inacurate slug.) So the only real difference between the Assault Rifle and the Battle Rifle is the round... and that the base Battle Rifle is much bigger (different frame) than the lighter Assault Rifle. The Sniper Rifle has been since the Vietnam conflict either an acurized Battle Rifle or a rebuilt Sport Rifle. The game assumes the former, but many of the weapons actually shown in SR4X are the later. Carbines, by modern reckoning, are forshortened Assault Rifles. A "carbine" Battle Rifle would be an Assault Rifle chambered for a Battle Rifle cartridge... ok I should add that as a speciffic option because there's an oddball version of the H&K G3 that just came to my mind, and the new LWRC S.A.B.R. I think fits that description as well. OK, easy to add.)

Shotguns are not just large-bore rifles. On the contrary, they have an entirely different set of constraints on their design due to the historically abnormal characteristics of their rounds. Yes, you can have a fully automatic Shotgun, but it's not just a big Assault Rifle or even Battle Rifle. It's bleeding BIG. Combined with the other odd characteristics, it suggests it is deserving of its own classification.

Machine Guns are not built like automatic rifles at all. Battle Rifles and Assault Rifles are designed for short periods of sustained automatic fire, not just limited by ammunition in their clips but by their breech and barrel designs as well. One of my complaints is that Shadowrun et all uses the old British designation system to classify Machine Guns, where it's more role than engineering and design. Since the 1980s, Light Machine Guns have fired Assault Rifle ammunition, Medium Machine Guns have fired Battle Rifle ammunition and Heavy Machine Guns have fired... well, big honking rounds like the .50 BMG. The actual philosophy behind the three is actually different as well, with the LMG not really being designed to handle the kinds of duration of fire in a defensive emplacement, being optimized to provide covering and suppressive fire for teams. MMGs are designed less for portability and much more for use in defensive emplacements or vehicle mountings which call for longer periods of sustained fire. HMGs are like MMGs but written very, very large.

By allowing for all the above general starting points and leaving space for different classes of rounds, you can essentially build any weapon you care to name. The only real exception is going to be something like the Beowulf conversion for AR-15/M-16 series weapons.

Firearm design is a very specialized branch of engineering, and I didn't want people to need to refer to a separate book for details to build a gun. I wanted enough detail to convey the reason different guns were made in different ways while still keeping the basic simple ideas in the system as presented in the core products. Put another way: when new guns come out, I wanted their conversion to this system to be quick and relatively easy.