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M1919A4 Prototypes
By Charles Brown

The story of how the M1919 Tank Machine Gun morphed into the M1919A2 as a result of the Cavalry and Infantry’s desire for a more readily portable automatic weapon is pretty well known by most Browning aficionados thanks to Dolf Goldsmith’s seminal work The Browning Machine Gun, Volume 1.

However there isn’t a lot of information and pictures of how the M1919A2 became the M1919A4. We hope to add a little background to this most interesting story.

When the M1919A2 was officially approved in June 1936 it was assigned the Major Item number 51-77. It took almost 6 years to produce a weapon differing from the M1919 Tank Gun only by the addition of front and rear sights, a new style buffer group, a sling attachment, and a new one piece aluminum stock.

While the A2 was being “developed” the Ordnance Department had arrived at the inescapable conclusion that the Tank Gun/A2’s 18 inch barrel did not develop the full ballistic potential of either the .30 Caliber M1906 or the M1 Ball cartridges.

The rather obvious fix to this problem was to make the barrel longer and about 24 inches give or take was what was already being used in other .30 caliber weapons. Instead of stopping development of the M1919A2 and taking heat from both the Cavalry, who started the ball rolling way back in 1930 and the Infantry who jumped on the air cooled machine gun bandwagon in 1931, Ordnance let it proceed to adoption while developing a 24 inch barreled improved version.

Because the A2 and the 24 inch barreled new and improved versions were both designed to be used on the new light weight M2 tripod which weighed one third as much as the M1917 tripod, Ordnance agonized over what turned out to be non-existent recoil/stability issues.

Some of this was brought about by still thinking of the machine gun in the context of an indirect fire weapon needing a very stable firing platform.

Much effort went into developing back plate recoil buffer systems for the M1919A2 involving springs and stops and muzzle “stabilizers”, actually a combination muzzle brake and booster that attached to the muzzle in place of the standard front barrel bearing and muzzle plug.

None of these devices were used on WWII production versions of the M1919A4 because the weapon was not employed in the manner envisioned for ground use in the mid 1930’s.

The two competing 24 inch barreled versions of the .30 Caliber air cooled machine gun were called “Browning Tank Machine Gun Cal...30 M1919 E2” and the “Browning Machine Gun Cal..30 M1919A2E3”.

The only real difference between these weapons was the front and rear sights.

The M1919A2E3 used the same sights as its parent with the front sight attached to a ring near the muzzle while the M1919E2 had its front sight attached to the front of the casing.

This difference in sight attachment also affected the rear sight graduations because of the difference in sight radius.

Both guns had all the era’s standard features, the reinforcing stirrup, dovetail style bottom plate with separate elevating bracket and a bolt latch.

The bolt latch was a “must have” holdover from the Tank guns. This feature was required because the tank guns evolved from the water cooled M1917 which fired from a closed bolt.

Cook-offs were not considered to be a problem in the M1917 because of the dissipation of chamber heat by the water cooling system.

This was not the case in the air cooled tank guns and the bolt latch was used to promote chamber cooling and prevent cook-off of chambered rounds.

By late May 1943 the bolt latch was done away with entirely.

Both styles of prototype weapons also had reinforcing applied at the rear of the side plates where the back plate slots were cut. How this reinforcing was attached is not clear.

Apparently this was thought to be a weak point which, according to one school of thought, was addressed by heat treating the rear most inch of the side plate on production versions of the M1919A4.

One feature that that the prototype A4’s had that the original A2 didn’t have was a new style belt lever pivot pin assembly adapted from the Aircraft Brownings featuring a nut and bearing with the pivot pin held in place with a cotter pin.

This style pivot pin replaced the pin with the flat spring used on the M1917 and the M1919 Tank gun and the A2.

Both prototype A4’s used the M1919A2’s buffer system that featured a spring, stop and spacer arrangement.

The A2E3’s front sight lost out, even with its longer sight radius, because it was easily damaged and interfered with mounting on some vehicles while the M1919E2’s front sight was mounted on the front of the casing.

There were many more improvements yet to come but at long last the basic weapon footprint was here.

Production was nearly halted on tank gun to A2 conversions, only about 1038 A2’s were actually produced.

By April 1937 the greatest single improvement to the Brownings arrived. Captain Walter P. Gorton’s flanged bottom plate which combined the reinforcing stirrup with an integral elevating bracket solved all those pesky side plate/bottom plate bulging issues. The 1937 prototype had a few other improvements.

The front sight was redesigned with elevation and azimuth adjustments and a folding feature for ease in packing the weapon.

A new rear sight mounted on a newly designed rear sight base riveted to the left side plate and calibrated 0 to 2400 yards for .30 Caliber M1 Ball ammunition with 0-90 mils elevation graduation on the left side of the sight leaf was provided.

Because of the new rear sight base the top cover latch now had a retracting handle riveted on.

The belt lever pivot assembly got another makeover, a new pivot bushing nut now having a spring steel cap that snapped over the bushing nut to retain the pivot pin.

The back plate buffer system dropped the tapered plug and split ring in favor of a filler piece that was supposed to prevent the “freezing” of the plug and ring.

March, 1938 brought a few more changes some adopted and going on to production and some dropped.

The top cover hold open device, a longer operating lug on the belt feed lever, slightly changed profile of the top cover latch retracting handle and the domed head rivets made the cut.

The small .617 inch orifice muzzle plug and heavier driving spring intended to increase the rate of fire to 500-600 rounds per minute, thankfully, did not.

While John Moses Browning was a genius, there are absolute limits to any engineering design.

Other than the slotted barrel jacket we now had the pre-production M1919A4.

The Ordnance Committee Meeting held on August 17 1939 took up Item 15286 “Browning Machine Gun, Caliber .30 M1919A2 &A4. Modification of guns of early manufacture.” The Committee noted that funds were now available to convert the 1038 A2 (18 inch barrel) and 525 early type A4 (24 inch barrel) for modifications , “which after having completed, will make all M1919A4 guns of uniform pattern and will eliminate the A2 gun having the 18 inch barrel and improvised sights.”

The sub-committee recommended approval and action by Industrial Services to modify the above mentioned guns.

Many more changes in materials and parts design, both for improved operation, material conservation, reliability and simplification of production were on the horizon, but for now, we had the basic ground weapon with which to gird our loins for the oncoming storm, flashing and rumbling away in the distance.

Just like the approaching thunderstorms, ominous but distant, that you remember as a small child, safe in your bed.


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