The Mk 19 Mod 0 had problems during its Vietnam war deployment and after a product improvement program from 1971 to 1972, six units were deployed with Naval riverine forces as the Mk 19 Mod 1. User improvements resulted in the Mk 19 Mod 2 being fielded in 1973. More user improvements resulted in a complete redesign of the Mk 19 during the years 1973 to 1976. The definitive Mk 19 Mod 3 was released for service in 1976. The Mk 19 Mod 3 was adopted by the USMC in 1982 and by the U.S. Army in 1983. The Mk 19 is a blowback operated and air-cooled. Its receiver resembled a shortened version of a .50 Browning machinegun without the barrel support and a short barrel.
The Mk 19 fires 60 rounds/minute in rapid fire and has a 325 to 375 rounds/minute cyclic rate. Its maximum range is 2,200 meters (2,405 yards) and a maximum effective range of 1,550 meters (1,695 yards). Muzzle velocity of the grenade is 790 feet/second. Overall length is 41.5 inches (Mk 19 Mod 3). Weight is 72.5 pounds (Mk 19 Mod 3), without mount.
The high-explosive, dual-purpose (HEDP) M430/M430A1 grenade can penetrate up to 2 inches of armor. The grenade has a kill radius of 5 meters (16.5 feet) and wounding radius of 15 meters (50 feet). Grenade arming distance is 15 to 30 meters (50 to 110 feet).
WARNING: The 40mm grenades used by the Mk 19 and M79/M203 grenade launchers are NOT the same. Grenades for the latter two launchers develop much lower pressures than those fired by the Mk 19. The M79/M203 grenade launcher barrel is aluminum, while that of the Mk 19 is steel. The Mk 19 grenade round is longer than those used by the M79/M203 launchers. Attempts to fire the Mk 19 grenade round in the M79/M203 launcher will destroy the weapon and damage or kill the operator.
Ammunition types are: M430/M430A1 HEDP; M383 HE; M385/M918 TP (target practice); M922/M922A1 dummy rounds. Links: steel, disintegrating M16A1 or M16A2. HEDP, HE, and TP ammunition is pre-linked in M548 boxes with 48-round lengths. The Mk 19 is a very significant boost to the firepower of a special warfare unit.
The cartridge the M14 was to use generated as much controversy as the weapon itself. The problem was the military wanted a full power .30 caliber round in a light weight weapon that would have full automatic capability. It just was not possible. The M14, at 750 rounds per minute in the full-auto mode, is very hard to control.
In the early 1950's, some countries were interested in developing a mid-range cartridge from combat lessons learned in WWII. It was concluded a select fire weapon, firing a mid-range round could replace the submachine gun and the full power battle rifle. The Germans had developed their own mid-range cartridge: the 8mm Kurz was utilized in their highly advanced (for the time) Sturmgewehrs MP 43, MP 44, and StG 44 in the closing months of the WWII. The Soviets developed their infamous 7.62 x 39 mid-range round and the SKS rifle which was succeeded shortly after by the AK-47. Great Britain was working on their .280 intermediate round for use in their version of the FN FAL. To the United States Military way of thinking the 7.62 x 51 was an intermediate round; after all, it was 12mm shorter than the .30-06 cartridge. At the period when the M14 was being developed, the NATO countries where trying to adopt a standard NATO cartridge. The reason was simple. In the event of another war, supplying allied armies would be much easier if they used the same ammunition. The United States insisted on, and got the 7.62 x 51 (.308) cartridge standardized as the NATO round. Ironically, many of the NATO nations adopted the FN FAL making it the most prolific rifle in the world chambered for 7.62 NATO ammunition.
The M14 was originally produced for the U.S. military by four manufacturers: TRW, Springfield Armory, Winchester, and Harrington and Richardson (H&R). The weapon was produced from 1957 until 1964 when the AR-15 (M16) was being considered and eventually adopted. Approximately 1,400,000 M14s were manufactured.
The M14 is basically a product-improved M1 Garand. The M14 cured the short comings of the 1930's-developed Garand. Briefly, these improvements were a detachable 20-round capacity magazine, a floating gas piston, the gas port on the barrel located closer to the receiver, a roller on the bolt to reduce friction, full-auto capability, a flash suppressor, chrome lined barrel, and a "smaller" round: the 7.62 NATO or as civilians were to know it, the .308.
The M14 was produced in several configurations. The M14A1 (E2) was developed to help control the weapon while firing in the full-auto mode. Some of the modifications made were a straight line stock with a pistol grip and a retractable fore grip, a muzzle brake, recoil pad, and a bipod. These improvements also added additional heft to an already heavy weapon. The standard M14 weighs in at 8.7 pounds empty and 12.75 pounds for the A1 version. A heavy-barreled version was contemplated as a possible Squad Automatic Weapon (SAW): it was to be the M15. After extensive testing it was concluded the M14 was not well suited to the SAW role, and the M15 was not adopted. Many standard M14s where issued with a selector lock that prevented the user from switching to the full-auto position. These locks could be removed if the situation warranted.
Another configuration of the M14 was the excellent M21 sniper version. This was probably the area for which the M14 was best suited. One version of the M21 used a Leatherwood ART scope (Auto Ranging Telescope). Earlier versions were equipped with the same M84 scope the M1 Garand snipers used. A few M21s were equipped with a Sionics sound suppressor. Although the 7.62 round is supersonic and not easily suppressed, it made the location of the shooter difficult to detect.
Yet, another version of the M14 was the National Match M14. These where hand assembled by military armorers using selected parts. The NM versions also utilized special sights, glass bedded stocks and other parts which had to meet very strict tolerances. The NM M14 is primarily for shooting competitions.