M1919 Top Cover and Feed System Development
By Charles Brown

The Model of 1919 Tank Machine Gun borrowed most of its operating features and design from the Model of 1917 water cooled Browning and passed them down the DNA chain to the M1919A2 and the M1919A4 and the rest of the family.

Besides just covering the top of the feed way, the Browning top cover mounts the parts that advance the feed belt, some of which were subject to more experimentation, modification, tinkering, and unintended consequences than Frankenstein’s monster.

Browning’s design converted the fore and aft reciprocating motion of the bolt under recoil and counter-recoil to a side to side mechanical force by the belt feed lever lug following a serpentine track cut in the bolt top. The other end of the belt feed lever acted on the belt feed slide and belt feed pawl that advanced the feed belt and also prevented double feeding in the event of a failure to extract a cartridge from the feed belt. It was both simple and complex all at the same time.

The tank gun top cover, even though it was on an air cooled weapon, required only a few changes from the Model of 1917. First the elaborate rear sight of the Model of 1917 and its base were eliminated and one of John Browning’s favorite designs, a pin secured with a flat spring used as the belt feed pivot was retained but the pin that locked into the rear of the water jacket base used as the top cover hinge pin was changed to a simple rod with a knurled head and secured with a cotter pin. Neither the Model of 1917 nor the tank gun had any sort of hold open device for the top cover. The rest of the feed system parts remained the same.

The pivot pin design was a model of simplicity. The pin had rectangular shoulders that dropped through mating cuts in the top cover, a quarter turn clockwise caused the shoulders to lock into the bottom of the top cover and the flat spring with a detent punch on the bottom snapped into dimple stamped into the top of the cover. This pivot was pretty much vibration proof and could be removed without tools. Browning used the same style flat spring pins to secure the gas tube and trigger guard to the receiver of the Model of 1918 Browning Machine Rifle.

Everyone involved in WWI took away the same message from four years of static trench warfare on the Western Front. The use of modern weapons had turned siege warfare into a highly efficient meat grinder that destroyed an entire generation of British, Commonwealth, and European male combatants with little to show for the carnage other than the casualty lists and who controlled a worthless moonscape of stinking muddy shell holes. No one in their right mind wanted a repeat performance.

With the war over and the National Army demobilized, the U. S. Army began to return to its nearly comatose pre-war state. Here and there some activity rippled the surface. One example is the U.S. Cavalry and later the Infantry adapting the tank gun to something more portable than the Model of 1917 and thought to be more useful in the next war, which was correctly thought to be a war of movement. This resulted in the M1919A2, which was basically the tank gun with different sights and a better mount – the M2 tripod – than the tank gun’s emergency tripod.

Circa 1930, Springfield Armory experimented with various improvements to the belt feed lever including one with a roller on the operating lug that rides in the serpentine track on top of the bolt. This sounds like a good idea, but nothing seems to have come of it, only a rather blurry drawing of this experiment survives, the date of which is illegible.

Nothing official was done with the tank gun top cover/feed system until the 1936 appearance of the prototype M1919A4’s now sporting a 24 inch barrel and a belt feed lever pivot pin assembly featuring a pin inserted through a bushing secured with a nut. A cotter pin on top of the nut secured the pin to the assembly.

According to the 1936 Notes on the Browning Tank Machine Gun, Cal. .30 M1919, E2 and Browning Machine Gun Cal. .30, M1919A2, E3 this change in pivot pins was made “to eliminate misfires,” however, a narrative on the development of the M1919A4 contained in the May, 1941 Standard Nomenclature List states that this modification was supposed to “provide for the assembly and disassembly of the belt feed lever from the top of the cover.” What benefit this change provided is far from clear as the original spring style pivot pin was also removed from the top.

Apparently the cotter pin style was not wholly successful and by 1938 the Ordnance Department had adopted a new pivot pin assembly featuring a spring steel cap that snapped over the newly designed bushing nut holding the now flat headed pivot pin in place. Through all this fiddling around with belt feed lever pivots, and a few minor dimensional changes in the belt feed lever, the top cover remained the same.

In June of 1940, Saginaw Steering Gear was finishing up its engineering, planning and production study to mass produce the M1919A4 when they noticed a problem during test firing. After closing the top cover three or four times after failing to align the operating lug of the belt feed lever with the serpentine groove in the top of the bolt, the spring steel cap popped off. If this went unnoticed and the operator kept firing one of two things happened either the pivot pin would walk its way up far enough to drop the end of the belt feed lever into the feed way or holding the lever up far enough that the operating lug would not engage the track in the bolt. The best case was it jammed the weapon the worst case was it broke the belt feed lever or damaged other components.

Saginaw produced a drawing of this event and forwarded it to RIA. For reasons not discernible, this drawing had B17503, the belt feed lever drawing number, hand written on it instead of the belt feed pivot assembly drawing number, the drawing got archived on 35mm film with the rest of the belt feed lever drawings remaining hidden away for nearly 80 years. So far the author has not found any documentation of RIA’s response to questions raised by this drawing other than the fact that the belt feed pivot assembly got another makeover.

This time instead of the spring steel cap, the bushing nut was made longer and threaded internally to take a slotted head cap screw with a locking (toothed) washer between the pivot pin head and the cap screw. Post-war an additional internally toothed washer was added under the bushing nut in lieu of staking the nut to the top cover. This system worked and lasted to the end of service life.

June 1942 found Saginaw producing cast parts made of their trademarked perlitic malleable iron alloy Armasteel for an endurance test at Aberdeen Proving Ground. One of the parts was a cast top cover that went into production mid 1943 off Saginaw’s own drawing. This casting reduced the number of assembly parts required for a M1919 top cover from eight to two.

There were three styles of top covers all sharing the same assembly drawing and stock number. Two were the conventional forged and machined covers assembled from the eight parts and one cast style with only two parts. The top covers were one of few M1919 parts requiring any hand fitting, the top rear of the latch plate sometimes needed to be touched up with a file to insure proper latch engagement.

Top covers with pivot pin assembly holes having the rectangular cuts and the spring locking dimple continued to be made well after the original spring style pivot pin was no longer available. Finally in December 1949 the pivot pin opening depicted on the drawings lost the shoulder cut and the spring locking dimple.

The belt feed slide and the belt feed pawl and spring remained virtually unchanged during their service life. The belt feed pawl design was particularly ingenious. The finger of the pawl rested on the top of the cartridge under the extractor; if the cartridge was extracted successfully under bolt recoil the finger dropped down allowing the stippled surface of the feed pawl to push the belt containing the next cartridge into position for the extractor to drop over for the next firing cycle. If the cartridge was not extracted from the belt the raised finger kept the belt feed pawl from advancing the belt.

In 1938, the familiar top cover hold open device using the fixed and movable spring tensioned plates on the bolt that served as a hinge pin for the cover was adopted. This allowed the top cover to be held in a 45 or 90 degree open position. This design provided a positive hold open feature for the M1919 cover without modifying the casing or the top cover.

Late in WWII and later in Korea it was discovered that the portion of the fixed hold open plate that rested in the right feed way caused links to catch on it and produced jams. This situation was remedied by a redesign of the short round stop to include a finger that covered this part of the plate. It is doubtful that the hold open device was adopted out of concern for the operator’s fingers getting pinched by a falling cover. More likely it was designed to make reloading or clearing stoppages easier because you no longer had to hold the cover open with one hand. The introduction of the M1919A5 in May of 1942 for use in the M3A1 light tank brought about a modified cover hold open device that mounted on the left side of the cover.

Elevation adjustable front sights were first detailed in drawings dated in May of 1946; however, so far our investigations have found no Modification Work Orders, or other directives, to replace the existing fixed elevation front sights that were issued until 1952. Apparently, in some cases, the new front sight, when folded into the storage position, struck the top cover in the open position. This resulted in the Ordnance Department deciding to correct this problem by cutting a half moon recess in the top cover. Some students of the Browning think that this alteration was initiated by the Israeli Defense Forces; it was a U. S. modification. It was merely a result of ordnance engineers failing to do what engineers are supposed to do; consider every possible eventuality.

In any event, after Korea and for better or worse, America’s policy was to arm everybody, and let God or some other higher power to sort the good from the bad and the ugly. As the perceived and demonstratively, at least for U.S. interests, the good which was Israel, our mid-east surrogate, got a boat load (actually several) of high quality combat tested weapons. The M1919A4 was the cream of the crop and the IDF got lots of them. The ever practical Israeli Defense Force out of necessity did some modifications to John Moses Browning’s timeless design, but this is a story for another day.

This article first appeared in Small Arms Review SAW (February 2013)
and was posted online on January 4, 2013


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