Description
U.S. MK 19 Mod 3 40mm Thumb Safety / SAFE–FIRE Selector, P/N 3269519
Item Overview
This U.S. military Safety, Thumb is the sliding SAFE–FIRE selector used in the sear assembly of the MK 19 Mod 3 40mm grenade machine gun. The compact steel component carries the stamped “S” and “F” position markings used by the gun crew. Moving the center tab from side to side controls an internal safety slide that either blocks or permits movement of the sear. This is an original gun-mounted component from one of the most recognized American crew-served weapon systems.
Identification and Features
Army, Navy, Air Force, and Marine Corps maintenance literature identifies this component as Safety, Thumb, part number 3269519. The repair-parts list places it within sear assembly 3269410 and assigns it NSN 1010-01-123-6079. The selector’s formed shape and raised center tab allow it to be moved laterally by the operator. Government specification data describes a steel component with a dark phosphate-type protective finish.
- Official nomenclature: Safety, Thumb
- Part number: 3269519
- NSN: 1010-01-123-6079
- Parent assembly: Sear Assembly 3269410
- End item: MK 19 Mod 3 40mm grenade machine gun
- End-item NSN: 1010-01-126-9063
- Selector markings: S for SAFE and F for FIRE
- Design reference: CAGE 53711
Historical Background
Part number 3269519 was standardized as an individual repair component for the MK 19 Mod 3 sear group. The multiservice maintenance manual lists it as item 9 in the repair-parts breakdown for sear assembly 3269410. Stocking the selector separately allowed military maintenance personnel to replace the control without discarding the complete sear housing and its other serviceable parts. The same repair literature supported MK 19 Mod 3 weapons used by the Army, Navy, Air Force, and Marine Corps.
Function and Operation
The thumb safety moves laterally and activates the safety slide inside the sear assembly. When placed on “S,” the slide blocks the receiver sear from being depressed by the operator, preventing the firing cycle from being released. Moving the selector to “F” withdraws that block and permits normal sear movement through the weapon’s trigger system. A spring-loaded detent holds the selector in position, while two slotted spring pins join the thumb safety to its matching safety-slide block.
Sear-Assembly Application
The MK 19 sear assembly fits into a cutout in the bottom of the receiver, with the thumb safety positioned toward the rear of the gun. The receiver sear holds the bolt to the rear until the trigger system releases it. The thumb safety controls whether that sear can be depressed, making this small component an important manual control within the firing mechanism. Part number 3269519 is documented specifically for the MK 19 Mod 3 sear assembly and should not be treated as a generic selector or ordinary stamped plate.
MK 19 Mod 3 Weapon-System Background
The U.S. military program that led to the MK 19 began in 1963 with work on automatic 40mm grenade launchers. The self-powered MK 19 Mod 0 followed in 1966, while improvement programs produced the Mod 1 in 1972 and the more reliable Mod 2 in 1973. A complete redesign in 1976 created the MK 19 Mod 3, which the U.S. Army adopted in 1983. The Mod 3 is an air-cooled, belt-fed, advanced-primer-ignition blowback weapon that can be employed from a ground mount or vehicle installation.
Mounting and End-Item Use
The MK 19 Mod 3 can be installed on an MK 64 carriage and cradle mounted to an M3 tripod, or fitted to compatible vehicle and table mounts. Army references document installations on the HMMWV, M113 family of vehicles, 5-ton trucks, and selected M88A1 recovery vehicles. The weapon provides automatic 40mm fire against personnel, fighting positions, and lightly armored vehicles. Its combination of explosive ammunition, belt feeding, and ground or vehicle mounting made it a flexible support weapon for infantry, military police, combat-support, and vehicle crews.
History of Use
Early MK 19 development was tied to the U.S. Navy’s need for greater firepower aboard riverine patrol craft, and the Mod 1 was used successfully in that role. The redesigned Mod 3 later entered broad service with the U.S. Army, Marine Corps, Navy, and Air Force. Army doctrine has employed the weapon for defense, patrols, rear-area security, urban operations, and special operations, while vehicle crews have used it as a mounted suppressive weapon. Official military photographs continue to document the MK 19 in mounted-gunnery instruction and live-fire training, showing the long service life of the system supported by this safety component.
Condition
This is a military-surplus thumb-safety component with the “S” and “F” selector markings that identify its purpose. Expect normal storage and handling marks, finish variation, light scratches, edge wear, or minor surface discoloration consistent with surplus parts. The listing is for the individual thumb safety; the sear housing, safety slide, spring pins, detent parts, and other sear-assembly components are not included unless specifically shown or stated. Refer to the inventory photographs for the representative appearance and condition.
Ideal For
This original MK 19 component offers a clearly identified example of the grenade machine gun’s sear and safety system. Its documented part number, stock number, and SAFE–FIRE markings make it well suited to focused military collections and historically accurate display work.
- MK 19 Mod 3 parts collections
- Museum and armorer-training displays
- Demilled or cutaway sear-group displays
- U.S. crew-served weapons collections
- Military parts identification references
Approx length 2.25", Approx width 0.5", Approx height 0.25", Approx weight 0.1lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item’s general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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