Which submachine guns are known to fire from an open bolt?

The submachine guns known to fire from an open bolt are specifically designed to have a unique firing mechanism that enhances reliability and cooling. In the case of the UZI, Thompson, and BAR, they allow for this firing method where the bolt is held to the rear, and when the trigger is pulled, the bolt moves forward to chamber a round and then fires it.

The UZI is a well-known submachine gun with an open bolt design that contributes to its simplicity and reliability. The Thompson, also known as the "Tommy Gun," features an open bolt mechanism which helps reduce the likelihood of cook-offs during sustained fire. The BAR, or Browning Automatic Rifle, while primarily a light machine gun, also utilizes an open bolt design.

This mechanism is particularly advantageous because it makes the firearm less likely to fire accidentally if dropped and also allows a cooling period between shots. In contrast, other firearms such as the M16 or AK-47 use a closed bolt design, which is common in rifles to enhance accuracy. Therefore, the correct option identifies submachine guns that are explicitly recognized for their open bolt operation, focusing on reliable performance in various conditions.