Osa (handgun)

Lore & Background

The Osa system was developed in the 1990s by G.A. Bideev and is produced by state-owned entities. The PB-4 is a four-barreled break-action gun with an aluminum chamber block containing two horizontal '8'-shaped chambers, each housing two rounds. The cartridge case itself acts as the barrel, with the bullet positioned deep inside; the front of the case is flush with the chamber block when in firing position. A four-fingered extractor in the central channel retains rimless cases and extracts them rearward for manual reloading. The trigger and trigger guard are fixed to the lower side of the chamber block.

The chamber block locks to a handle block containing the locking surface, firing button, pistol grip, battery, and electronics. Primers are ignited electrically via four circular contact plates and four contact pins. The electronic firing mechanism can send impulses sequentially to chambers 1 through 4 and skip malfunctioning rounds. Some models use a battery; others use a piezoelectric igniter similar to kitchen gas lighters. A simple sight assembly consists of a semi-cylindrical groove and a white forward post; some variants have a built-in laser sight with a laser window in the center of the locking surface, the beam following the central extractor channel. There is no safety switch—the weapon is always ready to fire when locked and loaded, provided the battery is not discharged (on battery-powered models).

A person shot from about 1 meter with an 18×45T Osa pistol to the temporal region of the head suffered a penetrative injury, with the bullet traversing most of the brain, reducing the victim to a vegetative state.

Reader's Guide

The Osa represents a distinct approach to non-lethal and multi-purpose handguns, combining a break-action multi-barrel layout with electronic ignition and a wide array of specialized ammunition. Its design deliberately uses the cartridge case as the barrel to discourage modification for increased power, reflecting a focus on civilian and law-enforcement safety. The system's ability to fire rubber bullets, pepper gel, flashbangs, signal flares, and illumination rounds from the same platform makes it versatile for self-defense, signaling, and crowd control. The Osa has been adopted by law enforcement units in Russia, Germany, Ukraine, Kazakhstan, and other countries, and a Brazilian variant (Defenzia) is used by the Pinal County Sheriff's Office in Arizona. The joint agreement between Osa and Defenzia in 2014 led to plans for assembly and manufacturing in Brazil and the United States, with a civilian 'M11' version in .50 caliber awaiting BATF approval. The Osa's legacy lies in its innovative integration of electronic firing, multi-chamber design, and non-lethal capability, though its use has also been documented in a severe injury case, underscoring the potential lethality of such weapons at close range.

Did You Know?

• The Osa's cartridge case has an external diameter of 18 mm while the bullet caliber is 15.3 mm.
• The electronic firing mechanism can skip chambers with malfunctioning rounds to avoid misfires.
• The PB-4-1ML model has a built-in laser sight and uses piezo priming.
• The Defenzia D-09 variant is 12 gauge and cannot load traditional shotgun shells.