Black Mesa (formerly Black Mesa: Source) is a fan project aiming to produce an enhanced version of classic FPS Half-Life in the latest version of the Source engine originally created by Valve for Half-Life 2. It began in 2004 when it became clear Valve's own game Half-Life: Source would be a port of the original rather than a full remake as some had speculated, and after many delays and some legal issues, Black Mesa was released on September 14, 2012. An enhanced version by the same name, using the 2013 version of Source as opposed to the original 2007 version, and including Deathmatch mode which the original release omitted, was released on Steam Greenlight on May 5th 2015. At present, both versions' singleplayer modes end immediately prior to the much-derided "Xen" segment: the developers have stated the 2012 version will never have this content released (though another fan group made an unofficial mod for the mod to add it), while more recently they have released in-progress map shots of Xen in the newer version, with a tentative release date of summer 2017: this has since been delayed to December 2017.
Alongside firearms, the game features fictional "experimental" weapons which won't be included in this page as they have no real-life counterparts.
The following weapons appear in the mod Black Mesa:
The standard pistol returns from the PC version, this time with tritium illuminated sights. The model's texture identifies it as a Glock 19, even though the pistol is modeled after the full-size Glock 17.
The Colt Python makes a comeback from the original game. On the side it says ".357 PYTHON". The secondary fire key toggles the iron sights with increased zoom. It is also worth noting that the screw placement above the trigger guard is completely wrong for a Python. When aiming down the sights, the firing mode seems to change from double-action to single-action, as Freeman can be heard manually cocking the hammer back after each shot while the cylinder rotates to the next chamber, although the hammer always remains in uncocked position.
Heckler & Koch MP5A3 with M203PI grenade launcher
The MP5A3 in the game is modeled after the weapon seen in End of Days, including the barrel shroud and M203PI grenade launcher. It is found in the hands of Special Forces in Chapter 5 and onward, and while it is automatic, clicking the mouse once will fire a 3-round burst. It should be noted that the front sight of the weapon lacks the sight post, and the reload animation is incorrect, as it shows the cocking handle locking back automatically and coming forward by itself when the magazine is released.
Like in the original Half-Life, the M203PI is never seen being reloaded; this time it comes with only three grenades instead of ten. Interestingly, the way these 3 grenades are fired successively is reminiscent of the Metal Storm 3GL.
The 2015 remake of Black Mesa has two reloading animations, one mid-magazine where the magazines are simply swapped (which can be difficult to do on an MP5 with a full magazine and the bolt closed, hence the usual HK slap) while the empty reload shows Gordon use his hand to lock the charging handle back before removing the magazine; he is shown riding it forward with his thumb rather than slapping it. The fire rate has been lowered, and the 3-round burst function at initial firing has been removed. There is still no reloading animation for the M203, Gordon simply swapping his grip from the trigger to the forend after each shot.
The SPAS-12 makes its return in Black Mesa. The one in Gordon's hands has no stock, but the world model of the shotgun still has the stock in folded position (granted, given how the weapon is never far enough from the screen to see so much as the pistol grip, one could argue that Gordon is simply the only person in the entire game smart enough to unfold the stock). Like in Half-Life and Half-Life 2, it has the unrealistic ability to fire two shells at the same time.
An unknown or composite magazine-fed crossbow appears in Black Mesa. Arguably one of the best weapons in the game due to its one-hit-kill capability on almost anything, it has a magazine capacity of 5 bolts and comes equipped with a scope.
Futuristic Armbrust ATW
The futuristic version of the Armbrust ATW seen in Half-Life returns in Black Mesa with similar functions. The alternate fire button switches between laser-guided mode and "blind-fire" mode. While it is fitted with what appears to be a telescopic rifle scope, this cannot be used.
Mk 2 Hand Grenade
The Mk 2 hand grenade can be found in abundance throughout the game as early as Chapter 3. Special Forces marines occasionally will use these to flush the player out of their hiding spot.
A backpack presumably filled with some type of demolition charges and rigged to a remote detonator is available.
A fictional mine based on the "laser tripbomb" from Duke Nukem 3D, which appears to have in turn been based on some kind of door keypad with a retinal scanner. While laser-activated mines do exist (mostly not for military purposes as they would be easily located with IR sensors, explode when it rained, etc), they typically require the placement of either a laser emitter which is separate from the mine, or a mirror to reflect the laser back into the device's detector. By itself, there would be no way for the mine to "know" the beam of light had been cut without either using a pulsed rangefinding laser instead of a continuous beam, or a fairly sophisticated imaging system linked to a camera monitoring the laser, and the imaging system of the latter could simply be used as a detonator itself. Laser traps also typically do not use visible-wavelength lasers, as fairness is not a major factor in their design.
M242 Bushmaster Chain Gun
The M242 Bushmaster Chain Gun is mounted on LAV-25s, which replace the M2 Bradley IFVs from the original game as the United States Marine Corps utilizes the LAV; the Bradley is used by the US Army.
The strange cannons found in the original Half-Life are replaced with tripod-mounted BGM-71 TOW launchers. Their depiction is very unrealistic: as well as the obvious lack of a 1.5 second firing delay, the spent tube simply vanishes when the missile is fired. There is an unusual bit of realism in that the player then has to locate a new missile tube and place it in the launcher manually.
The Browning M2HB appears as a usable emplaced weapon in the mod. It is mostly seen in small fortified bunkers mounted on tripods. All the M2s have unlimited ammunition and can completely dismember aliens and humans with one shot. Special Forces marines may use the weapon against the player if it isn't already occupied. It is also mounted on the commander's hatch of Abrams tanks.
M230 Chain Gun
The M230 Chain Gun can be seen mounted on Apache helicopters.
LAV-25s and M1 Abrams main battle tanks mount a coaxial M240C machine gun.
An M240D machine gun is mounted alongside the M2HB on Abrams tanks.
Heckler & Koch MP5A5 with GP-30 grenade launcher
The Heckler & Koch MP5A5 with a Russian GP-30 grenade launcher, RIS handguard, EOTech holographic sight and MP5K-PDW-style side-folding stock was cut from the final version of the mod, with the MP5 included simply being a recreation of the model from the original game. (Note that the M203 or GP-30 launchers are not capable of being mounted on an unmodified MP5 variant in real life.)
M4A1 with M203 Grenade Launcher
The M4A1 (substituting the Model 727 seen as the HD and PS2 replacement of the MP5 in the original game) was cut from the mod during development.