From Black Mesa: Wiki

A render of the shotgun old model. The stock has been removed in the current model.

Overview

The SPAS-12 is a single barrel, dual-mode combat shotgun that comprises one part of Gordon Freeman's arsenal. It is used as an emergency weapon by the Black Mesa security guards, as well as one of the primary weapons of the military forces sent to the facility soon after the resonance cascade. It can first be found in Office Complex, but if missed, appears in We've Got Hostiles.

The SPAS-12 in Black Mesa holds 8 rounds with a reserve of 64 cartridges [1].

Primary Function

The SPAS-12's primary fire discharges a single shell of 12 gauge buckshot. Useful against enemies at close-range to (almost) medium-range.

Secondary Function

The SPAS-12's secondary fire discharges two shells in rapid succession. This attack is very powerful and does a large amount of damage to very close-range enemies. However, the resulting recoil is great which can leave the player vulnerable.

Trivia

• It is possible to gib enemies with the shotgun, but this feature is disabled by default. It can be re-enabled with the use of convars [2].
• The SPAS-12's "second barrel" is actually the internal tube magazine, where the shells are loaded and stored until being chambered and fired.
• The SPAS-12 is usually fired in semi-automatic, while pump-action is used to fire low-pressure shells such as less-lethal beanbags or tear gas shells.

Redesign History

The SPAS-12 shotgun originally had a folding stock folded up on the top of the shotgun, as per the Half-life HD pack, but the developers decided to remove the stock, to keep it more in line with Valve's original shotgun model, as well as make it more aesthetically pleasing.

The model has been recently redesigned [3] and rebuilt with higher-poly geometry and higher-resolution textures [4], based in a model made by Pontus Ryman [5].

The SPAS-12 old model, made by Stimor.

An early in-game screenshot of the SPAS-12, with stock attached.

In-game screenshot of the SPAS-12 with the folded stock no longer attached. That model has been replaced with a new model, not shown to the public yet.

Ditto.