The CMP has the fastest reload time of any SMG (very nearly the same speed as a pistol), a high fire rate, and good total ammo. The downside to the high fire rate, though, is the unpredictable recoil it shares with the Mark 10. It will often recoil to the sides and downwards. This can make it difficult to use for someone who's not used to this unpredictability.
All these things, combined with the slightly obstructive iron sight, make the CMP strictly a close-range weapon. With certain attachments, you can reduce the recoil to allow it to perform better at medium-range situations. A skilled user can absolutely devastate groups of weak enemies when the time is right. With the necessary attachments, the CMP becomes a good all-around weapon for any heist, having the high RoF of the Mark 10, the ammo pool of the Blaster 9mm, damage of the Para, and accuracy of the Kobus 90.
The CMP is based on the Brügger & Thomet MP9-NA3. It can be easily differentiated from the parent weapon by it's lack of a front grip, with an under barrel grip-less rail in it's place. The sideways folding stock and top rail mount featured on the CMP are also parts native to the MP9. Attaching the Skeletal Stock turns it into the MP9-NA4.
The stamping on the left side of the weapon confirms that the CMP is a MP9, though the first letter of the stamping is partially hidden by the rail mount so it is hard to tell which specific model the weapon is. The side rail is also unusually located to the left of the CMP rather than on the right like the real-life MP9.
The CMP lacks a fire-selection dial on its left side, meaning it should not be able to alternate between semi-automatic and fully-automatic fire like depicted in-game, but rather uses an old-model double-stage trigger to produce either single shots or automatic volleys.
"CMP" is most probably a reference to the CMP-150, a similar weapon found in the Nintendo 64 video game Perfect Dark, which was based on Steyr TMP, the parent design of the TP9/MP9.
The CMP's default magazine holds an impossibly large total of 30 rounds, despite being modeled after a 15-round unit. Likewise, its Extended Mag also contains a whopping 12-round addition.
Despite being a machine pistol, the CMP is classified as an SMG in-game.
The CMP shares its firing sounds with an unsuppressed SpecOps.
In one of the early builds of Payday 2, FBI Shields used a CMP with a folded stock, a mod unobtainable by the player. This specific CMP can be viewed in the launch trailer of Payday 2, seen from 3:32 - 3:35.
The Stubby Compensator could not be installed to the CMP until Update #10, making it the only weapon that could use some but not all of the standard barrel extensions.
The inventory icon of the weapon shows the gun with the Extended Mag and without the foregrip, which was added in Update #9.
Prior to said update which gave the CMP a foregrip, the weapon shared its first person idle animation with the Mark 10.