Guns
Default: DX-4.
This is the ability to use a hand-held chemical-propellant or mass-driver projectile weapon. Roll against Guns skill to hit your target.
Make an IQ-based skill roll to take immediate action (e.g., eject a dud round), should your weapon fail.
You must specialize by weapon type. The available specialties vary by TL, but include one or more of:
Grenade Launcher (GL): Any large-bore, low-powered small arm that fires a bursting projectile. Includes under-barrel grenade launchers, flare pistols, and ultra-tech "tanglers."
Gyroc: Any kind of small arm that fires miniature rockets.
Light Anti-Armor Weapon (LAW): All forms of rocket launchers and recoilless rifles.
Light Machine Gun (LMG): Any machine gun fired from the hip or a bipod.
Musket: Any kind of smoothbore long arm (usually, but not always, a black powder weapon) that fires a solid projectile.
Pistol: All kinds of handguns, including derringers, pepperboxes, revolvers, and automatics, but not machine pistols.
Rifle: Any kind of rifled long arm – assault rifle, hunting rifle, sniper rifle, etc. – that fires a solid projectile.
Shotgun: Any kind of smoothbore long arm that fires multiple projectiles (flechettes, shot, etc.).
Submachine Gun (SMG): All short, fully automatic weapons that fire pistol-caliber ammunition, including machine pistols.
Most of these specialties default to one another at -2, but defaults involving GL, Gyroc, or LAW are at -4 in either direction. The weapons covered by each specialty vary by TL. For example, Guns (Rifle) covers muzzle-loaders at TL4, lever actions at TL5, and self-loaders at TL6+. In particular, ammunition varies with TL, from black powder and loose shot at TL4, to smokeless powder cartridges at TL6, to power cells and metallic slivers for TL9+ electromagnetic guns.
Familiarity is crucial here! Guns (Rifle) covers both bolt-action 12.7mm sniper rifles and 5.56mm assault rifles, but going from one to the other gives you -2 for weapon type (12.7mm to 5.56mm), -2 for action (bolt-action to self-loader), and -2 for grip (bipod to hand-held), for a total of -6 to skill until you familiarize yourself with all the differences.
Modifiers: All applicable ranged combat modifiers; -2 for an unfamiliar action (e.g., an automatic when you're used to a revolver) or grip (e.g., a shoulder-fired antitank weapon when you're used to a bipod), or for an unfamiliar weapon of a known type (e.g., a 5.56mm rifle when you are used to a 7.62mm rifle); -4 or more for a weapon in bad repair.