The UMP is a submachine gun built largely with polymer components, originally designed by Heckler & Koch in the 1990s as a cheaper alternative to the ever-popular MP5 submachine gun. Rather than replace the MP5, the UMP has instead become a complement to it in many cases.
The UMP fires at a rate of approximately 650 rounds per minute, or 600 in the case of the UMP45 (chambered in .45 ACP). This reduction when compared to the MP5 at approximately 800 rounds per minute is to mitigate the heavier recoil of the larger ammunition. It is often used when larger caliber ammunition is desirable, as the two MP5 variants chambered for calibers larger than 9mm Parabellum were discontinued in 2000. While a 9mm UMP exists, and is actually lighter than an MP5 due to the heavy incorporation of polymers, the MP5 generally fills this spot in games due to its higher rate of fire and ubiquity.
Because it is a less common weapon than the MP5 and often considered superfluous when the MP5 is included, it shows up in less games than the MP5. It typically appears in shooters featuring police/SWAT or counter-terrorist themes.
In Bad Company 2, the UMP .45 is not encountered during the Campaign missions. It is the final unlock for the Engineer class, and comes with the standard 25-round stick magazine used with the UMP .45. Ultimately it is arguably one of the poorer unlocks in the game, as you technically have unlocked the UMP .45 before. It shares the exact same stats with the 9A-91 Avtomat, and the SCAR-L. For this reason the SCAR-L is a better choice than the UMP .45 regardless of in-game experience, as it has a larger magazine. The only real reason that players use the UMP is for the SPECACT version made available as DLC. The SPECACT weapons come with additional achievements, meaning that the UMP .45 is really only used for this purpose.
Arguably, one of the weaknesses of the UMP .45 is the iron sight. However, the majority of players choose to use an optic on the Engineer weapons, meaning that this may not be a problem at all. Like the two similar weapons in-game, the UMP .45 can be operated with success when an ACOG Scope is fitted.
The UMP .45 is one of the two starting SMGs, alongside the MP5k. However, the UMP .45 is much more commonly
encountered online due to the fact it has extremely high damage, and an easily controlled recoil. The UMP .45 appears in Campaign, Spec Ops, and Multiplayer modes, albeit with slight changes for Multiplayer. In Single Player the UMP has a 25 round magazine and virtually no recoil. For this reason it can be advantageous to use the UMP .45 with an ACOG Scope when it can be acquired.
In online play, the UMP .45 is commonly referred to as a 'noob' gun, much like the ACR. Online, the UMP .45 has a 25-round magazine, and increased recoil. The weapon is more frequently silenced when used by other players, as the high damage of the UMP and the low drop off make it an ideal weapon for almost all ranges in some gamers' eyes. The UMP kills in around two or three shots, and is not necessary to use with Stopping Power, as this does not decrease the number of shots required. In Hardcore modes the UMP .45 can score a single-shot kill occasionally, and for this reason it is occasionally seen with an ACOG Scope to make it more easily aimed from longer distances.
Unlike other SMGs, the UMP .45 is absolutely terrible when dual-wielded, due to the lower fire rate. It is also highly inaccurate when fired blindly, and it is all in all, an undesirable choice for dual-wielding classes, where higher rates of fire to overwhelm the enemy trump a high powered round.