An M1911-A1, possibly based off the Springfield Armory M1911-A1 is the backup handgun for all human players. A second one can be found randomly in-game and dual-wielded, though the second will lack an attached flashlight.
These 1911s have 15-round magazines (even though the magazines being loaded into them are standard single-stack magazines that, at most, have 9 rounds in them) and never run out of ammo (see screenshot below).
The shotgun seems to be modeled squarely from a High Standard Model K-1200 Riot Deluxe Model, but has the trigger guard of a Remington Model 870 Shotgun and an Ithaca 37 magazine tube. Francis uses this weapon in the intro cut-scene and during the game. The receiver has the fictional make of the shotgun named as "Renegade Rangemaster". It should noted that the developers meant it to be an ambiguous pump-action shotgun.
A full-sized Uzi using a 50 round magazine (modeled after one using a 32 round magazine), with a flashlight taped to its handguard; is a First Tier automatic weapon. It's also Louis' main weapon in the cinematics.
The M16A2 is a second tier weapon with a 50-round magazine (Modeled after a standard 30 round magazine) and a flashlight clipped to its foregrip.
The weapon in the game is fully automatic, though the real M16A2 fires only in semi auto and 3-round bursts -- It's the A1 or A3 that's Full auto capable. This suggests that the weapon is an M16A2 with an M16A3/A1 upper receiver. It's Bill's main weapon in the intro cinematic, and both Bill and Louis will pick them up if they find them during the game.
Another Second Tier weapon, The Benelli M4 Super 90 has a 10-round magazine (even though the real one only has a max capacity of 7, or in this case 4, due to the civilian legal 4-shot magazine tube) and a flashlight clipped in front of the handguard. Francis will use it whenever he finds one.
The Ruger Mini-14 Ranch Rifle is a second tier gun with a magazine capacity of 15 rounds. The stock design suggests that its a pre-2005 model. Strangely enough, the Rifle combines the old, single-bladed front sight with a John Masen flash-hider and the post-2005 aperture rear sight. It's Zoey's preferred gun in the game. It should also be noted that there is a large overlook for the Mini-14. Ingame, it is called a "Hunting Rifle", but in Pennsylvania, it is illegal to use semi-automatic rifles for hunting.
A GE M134 Minigun, mounted on a monopod and set up behind sandbags, is usually found at the end of a campaign. It shreds almost all infected to pieces in seconds.
Despite its multi-barrel operation design to prevent this, it overheats presumably for game balance reasons. It appears to be rendered with a 200-round ammo can which would last it all of four seconds in real life.
The spade grips are mounted higher than normal in relation to the gun because they are attached to the same custom frame used for the Terminator 2 and Predator handheld Miniguns (minus the chainsaw grip/M60 handguard), rather than an actual Minigun mount.
Error creating thumbnail: File missingGeneral Electric M134 with first pattern spade grip mount and crosshair sights. Note the lack of flash suppressor and three disked barrel cluster - 7.62x51mm NATOThe GE M134 Minigun used in the game. Note the y-shaped frame on the top of the weapon that is modeled after the custom frame from the hand held Stembridge Minigun.
