The Heckler & Koch MP5, simply known as the Submachine Gun or SMG, is a weapon featured in Half-Life and its expansions. The primary weapon used by the HECU, it is an automatic weapon with a high rate of fire. It is also equipped with the 'Shorty' version of the M203 grenade launcher that boosts its effectiveness.
The attached grenade launcher fires powerful explosives that will automatically explode when hitting the ground. It does not need to be reloaded, so the player can fire as many grenades as they want until they run out of ammo for it.
Both the MP5 and the Glock 17 use 9x19MM Parabellum and share the same ammunition reserve, making the MP5 and the Glock 17 very easy to find ammunition for.
This weapon is first obtained at the start of the Half-Life chapter "We've Got Hostiles". It can be found next to a dead HECU soldier in the first room that has sentry guns. After that, it can be found in areas controlled by the HECU and picked up from dead HECU soldiers.
When a player picks up an SMG for the first time, it will have 25 rounds in its magazine. The player must reload the gun to get 50 rounds in the magazine. However, in some related games such as Half-Life: Day One and Half-Life: Opposing Force, the MP5 already holds 50 rounds when picked up.
When the Half-Life High Definition Pack is enabled, the MP5 becomes an M4 Carbine Assault Rifle. However, this does not change its accuracy and shared ammunition with the Glock.
The MP5's accuracy is suitable for short to medium combat ranges, but has poor accuracy at longer ranges, so it is recommended to use five round bursts for long range. However, since the recoil was increased in Half-Life: Source, it is no longer effective against a target at long range.
The player should be sure not to use the MP5's bullets against large groups of enemies for the MP5's bullets do only 5 points of damage. Save the bullets and fire the MP5's grenade launcher instead.
Groups of weak enemies, such as Headcrabs or Houndeyes, can easily be killed with the MP5.
The MP5 is effective on small groups of Vortigaunts and HECU Marines. With Vortigaunts, one should remember to move often to avoid being hit by the Vortigaunts electric bolts. With HECU soldiers, one should stay out of their effective range or make use of cover, since they have the same SMGs and slightly better accuracy.
The Alien Controller is easy to kill with the SMG. Since its bullets hit instantly, the player can attack the Controller and avoid its plasma balls with ease.
The SMG's accuracy is not affected by crouching, although it decrease some recoil in the Source version.
In multiplayer, the MP5 is more accurate, though the opposite was true in early versions of Half-Life.
The grenade launcher should be used to clear out large groups of enemies at once. One grenade can kill up to five HECU soldiers with ease if it lands in the center of the group.
The grenade launcher is also effective against enemies that have a lot of health, such as the Alien Grunt. One grenade can usually kill it in one shot. If not, it only takes a few shots from the SMG to finish it off.
Using the grenade launcher against weak enemies, such as Headcrabs, is obviously effective but is a waste of ammunition (unless it a group of Headcrabs). Melee attacks or normal bullets from any weapon are more advised.
The grenade launcher is one of the few weapons that can damage a Gargantua, so one should stock up on its ammo when wanting to kill a Gargantua manually.
If the grenade launcher is used at long range, intelligent enemies can usually run away from it before it explodes. Therefore, getting closer to the intended victims before firing is advised, as it prevents them from running away. However, being too close will affect the player's health, as with all explosive weapons.
Early textures for the MP5 can be found in the Half-Life SDK files.
The MP5 originally used 30-round magazines (which are far more common in real life). It was changed to 50 in the final game.
The Half-Life: Day One viewmodel is different from the retail model, however this can be only seen through a model viewer. The left arm is bugged and its only polygon is always attached to the magazine, and there's chrome on left arm instead of red stripes.