May 1, 2024

Firearm familiarization for the TALEM Professional – the Submachine Gun

It is important for tactical and law enforcement medicine (TALEM) physicians and medical personnel to be familiar with the weapons systems utilized by LEOs and SWAT units. Whether rendering a weapon safe prior to medical care, or using a weapon to defend patients and teammates, tactical medical providers must be able to handle and deploy the tactical tools carried by SWAT operators. The four categories of firearms used most often by LEOs are pistols, shotguns, rifles, and submachine guns. This article will cover the important facts and functions of the submachine gun by LEOs in tactical operations.

Submachine Gun

A submachine gun (SMG) is a magazine-fed selective fire automatic carbine designed to fire handgun cartridges. The term "submachine gun" was initially named by John Thompson, the inventor of the Thompson submachine gun, to describe its design concept as an automatic firearm with notably less power than a machine gun (hence the prefix "sub-"). By definition, a machine gun must fire rifle cartridges (with higher velocity than pistol ammunition) to be classified as such.  Submachine guns then are compact, selective-fire weapons chambered for pistol ammunition such as 9mm, 10 mm, or .45 ACP.

The submachine gun was developed during World War I (1914–1918) as a close quarter offensive weapon, mainly for trench raiding. At its peak during World War II (1939–1945), millions of submachine guns were made for assault troops and auxiliaries, whose doctrines emphasized close-quarter suppressive fire. New submachine gun designs appeared frequently during the next 40 years (Cold War), especially among special forces, covert operation commandos and mechanized infantrymen. Specialized variants were developed that were extremely compact or have extremely quiet operation.

Internal operations of the firing mechanism of SMGs can vary greatly. Some fire on an open bolt. Some are recoil driven, while others use mechanisms like a roller-delay system. Loading, unloading, and maintenance  of these weapons may require additional training, even for someone familiar with many firearms.

In the United States, submachine guns have sometimes been associated with organized crime, criminal gangs, and violence. The use of Thompson submachine guns by the Chicago Outfit and notorious bank robbers in the 1920s and 30s, as well as numerous Hollywood and real life uses of weapons like the Uzi or MAC-10, has contributed to the stereotype.

Submachine gun usage for frontline combat soldiers decreased in the 1980s and 1990s, and by the early 21st century, submachine guns were largely replaced by assault rifles firing a compact rifle cartridge (such as the 5.56 NATO /.223 round) which have greater effective range and can overcome armor.

Submachine guns are still used by security forces, police tactical units and bodyguards for close quarters combat due to their compact size and ease of control. Pistol caliber ammunition are quieter, have less recoil and muzzle blast, which is advantageous in close quarters. These advantages can be further enhanced with use of suppressors. These abilities are still valued during dynamic entries, rapid room clearing, and in specialized protection roles.

Naming Conventions

There are some inconsistencies in the classification of submachine guns. British Commonwealth sources often refer to SMGs as "machine carbines". Other sources refer to SMGs as "machine pistols" because they fire pistol-caliber ammunition. The term "machine pistol" is also used to describe a handgun-style firearm capable of fully automatic or burst fire, such as the Beretta 93R, Glock 18, and the H&K VP70. Also, intermediate-caliber weapons such as the FN P90 and H&K MP7 are often called submachine guns. In addition, short-barreled assault rifles such as the CAR-15, H&K53, and Mk18 (chambered in 5.56) have been historically referred to as submachine guns as they served in the latter's role.

Firearms that are visually comparable to SMGs but which are only able to fire as semiautomatic weapons have become increasingly popular among civilians. These are usually referred to as pistol caliber carbines (PCCs). Due to overall length or barrel length restrictions under the National Firearms Act (NFA) these weapons are often sold with longer barrels or no shoulder stock when compared to the military and law enforcement versions. Some fully automatic SMGs are available to civilians as transferable NFA items if they were manufactured and registered before 1986.

Common Submachine Guns in SWAT Operations

Some of the common SMGs used by SWAT teams include the H&K MP5, H&K UMP, B&T APC9, and the FN P90. These weapons are known for their reliability, accuracy, decreased recoil, compact size and ease of handling in high-stress situations.

  1. H&K MP5
    The Heckler & Koch MP5 is one of the most iconic submachine guns used by SWAT teams worldwide. It is known for its accuracy, low recoil, and modular design. The K version is extremely concealable, while the SD variant is extremely quiet.
  2. H&K UMP (Universal Machine Pistol)
    The UMP is another firearm produced by Heckler & Koch and is considered a more modern alternative to the MP5. It is offered in multiple calibers and with multiple customization options, allowing agencies to field an SMG in their chosen pistol caliber.
  3. B&T APC9
    The APC9 was adopted by the US Army in 2019 as its Sub-Compact Weapon (SCW). It is available in a variety of configurations including versions that take magazines compatible with common duty weapons. Similar to the MP5 it is offered in K and SD configurations.
  4. FN P90
    The FN P90 is a unique short bull pup-style submachine gun known for its innovative compact design and high-capacity magazine. It is chambered in 5.7x28, a small caliber, high-velocity bottleneck cartridge that has improved terminal performance against soft body armor.


SWAT teams play a critical role in ensuring public safety during high-risk incidents. The use of submachine guns is just one aspect of their specialized training and equipment. The selection of submachine guns is based on their suitability for close-quarters combat and the specific requirements of the mission. As law enforcement tactics and technology continue to evolve, SWAT teams will continue to adapt their training and equipment accordingly.  All tactical medical personnel will benefit by familiarization and competence with pistols, shotguns, rifles, submachine guns, and other weapon systems utilized by their local tactical teams.

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