Page "Firearm" Paragraph 58

Submachine guns were originally about the size of carbines.

Because they fire pistol ammunition, they have limited long-range use, but in close combat can be used in fully automatic in a controllable manner due to the lighter recoil of the pistol ammunition.

They are also extremely inexpensive and simple to build in time of war, enabling a nation to quickly arm its military.

In the latter half of the 20th century, submachine guns were being miniaturized to the point of being only slightly larger than some large handguns.

The most widely used submachine gun at the end of the 20th century was the Heckler & Koch MP5.

The MP5 is actually designated as a " machine pistol " by Heckler & Koch ( MP5 stands for Maschinenpistole 5, or Machine Pistol 5 ), although some reserve this designation for even smaller submachine guns such as the MAC-10 and Glock 18, which are about the size and shape of pistols.