The Compact-5 has the second highest total ammo out of all the fully-automatic secondary weapons, behind the Cobra. It has average damage, good stability, and decent accuracy, making it very ammo efficient compared to other automatic secondaries like the Para and the STRYK 18c. It can also achieve the maximum concealment rating, making the Gruber Kurz nearly obsolete, since the Compact-5's statistics are so similar.
Although it has a low rate of fire and low damage per second compared to most other secondary submachine guns (only the Para SMG and Swedish K are slower), its generous maximum ammo lasts long enough to make heavy use of during longer heists to save primary weapon ammo for stronger enemies. With the addition of the Straight Magazine, the Compact-5 can deal out considerably more damage at the cost of stability.
One of the main detriments to the Compact-5 is its tight rear sight, which is similar to the JP36 and significantly obstructs the player's view making it hard to get head shots at range. A sight attachment can dramatically improve the player's aim.
An extremely stealthy suppressed build is possible, offering a concealment stat of 30, but dealing only 31 damage per shot (40.3 with Silent Killer aced). If one desires, they may equip the Auto Fire mod to bring up the Compact-5's damage to 32 (41.6 with Silent Killer aced).
Although the main flashlight has a toggle switch, the laser sight component of the LED Combo is pressure-activated, meaning the laser will stay on as long as the pressure switch is depressed. This switch is not placed where it should be, however (on foregrips, magazine wells, etc...) and is instead ziptied to the main taclight, leaving no plausible mean for the user to toggle it without awkwardly moving their off hand off the weapon and gripping the attachment itself.
Upon release, the default reticle of this sight was a chevron instead of the retail version's red dot. After the release of the Gage Mod Courier DLC, it was reverted to the regular sight's red dot.
It is functionally the same as the standard Military Red Dot Sight, but the sight's casing is tan instead of black with the line "A-10" scrawled on near the adjustment knob. The sticker on the lens cap's interior also says "I <3 Payday" instead of having a picture of an American flag.
This sight was based on the Aimpoint CompM2 optic. While it is portrayed as a high-zoom scope in-game, the CompM2 is actually a reflex sight, meaning it offers no magnification in reality.
The Compact-5 is based on the MP5A4, as evident by its 4-point fire selector and fixed stock.
Adding The Ninja Barrel turns it into an MP5SD5, the Adjustable Stock transforms it into an MP5A5, having both makes it an MP5SD6, the Sehr Kurze Barrel coupled with the Bare Essentials Stock converts it into a MP5KA4 sans the foregrip, the Ninja Barrel with the Bare Essentials stock turns it into the MP5SD4, and the Sehr Kurze Barrel with the Spartan Stock from the Gage Spec Ops Pack turns it into the MP5K-PDW, albeit without the longer barrel and vertical foregrip. With the Straight Magazine, introduced in The Butcher Mod Pack 2, the Compact-5 gains the look and larger ammunition of the MP5/10, though is still a regular MP5 variant due to the MP5/10 featuring a bolt lock and release system, which the Compact-5 doesn't have.
Additionally, the Compact-5s used by the various enemies in the game are modeled after the MP5A3, as evident by their Safe/Single/Auto trigger groups.
The Compact-5 is also used by a subtype of Zeal Force combatants. Despite being shown with The Ninja Barrel on the announcement site, the in-game unit wields the Compact-5 with a Polizei Tactical Barrel instead.
The Compact-5 normally fires in full-auto during gameplay despite it being visibly set to 3-round burst operation.
The "safety" function is absent on the weapon model, with the semi-auto selector option being painted white to replace it. With the Nightstalker skin applied the MP5A4 fire selector is correctly depicted, however.
The player can perform a tactical reload with the Compact-5 despite it being impractical and awkward in reality. Due to how the bolt of the MP5 was designed, it will ride directly on top of the feed lips when the weapon is in battery, thus obstructing the new magazine's entry and preventing the user from properly seating it (if fully-loaded) when there is a round in the chamber. Tactically reloading the MP5 is in no way impossible, but will require the user to either load it with an incomplete magazine or risk a longer top up by locking the bolt back first and then load, usually losing the chambered bullet in the process.
The Cloaker uses a unique Compact-5 modified with the Sehr Kurze Barrel, Assault Light, Tactical Laser Module, Adjustable Stock, black Straight Magazine, and See More Sight. It also features its own unique modifications which are a vertical foregrip under the barrel and a unique Suppressor.
The obstructive iron sight of the Compact-5 is actually a two-option adjustable diopter drum rear sight, with the second option being more akin to PAYDAY: The Heist's iteration. The PAYDAY 2 variant is used for long-ranged precision firing, thus providing much less eye-relief compared to the other version.
The magazine bears real life markings to the real weapon. This is possibly a mistake, as it's doubtful H&K would allow their likeness used without license.
Additionally, "For law enforcement and federal use only" is printed on the magazine. This suggests that the weapon was stolen from a police or FBI armory.
There is a drum magazine for the Compact-5 in the games files which is most likely based on the GSG 5 .22 - 110 Round Magazine. It is accessible only by editing the games files. Functionally, this mod is similar to the CAR Quadstacked Mag in that it increases the weapon's magazine capacity greatly, making it akin to a Light Machine Gun, but with no movement penalty. A similar drum mag can be seen as part of the Sentry Gun feeding system. It is not fully known why the drum mags have been disabled for all the weapons other than the game's engine cannot switch between reload animations for each magazine modification on the same weapon.