TOP COVER LATCHES AND TOP PLATES FOR CALIBER
.30 AIR COOLED BROWNING GROUND TYPE MACHINE
Any discussion of the M1919 family of
weapons always begins with a short history of weapons
original M1919’s were designed from the M1917 water cooled model
and used to provide machine gun armament for WWI tanks.John M. Browning used the casing assembly of the M1917
and added an 18 inch barrel covered with a jacket with elongated
The purpose of the jacket was to hold the
"muzzle attachment" and “muzzle plug” later known as a
front barrel bearing and booster plug and provide support for
the much heavier barrel required by the loss of efficiency of
the water cooling system present on the M1917.
The muzzle plug/booster provided additional gas pressure thrust
on the front of the barrel to provide assistance to the recoil
operated M1917 mechanism now laboring with a decidedly heaver
group of recoiling parts.
The Armistice ending combat operations in WWI was signed before
very many of these weapons were produced.
If the U.S. Army learned anything from combat experience in WWI
it was that automatic weapons had changed the face of ground
The Cavalry arm of the Army also discovered that
to remain relevant they needed a way to increase combat power of
The Cavalry needed to add readily portable automatic weapon to
their TO&E (Table of Organization and Equipment).
The Cavalry’s first attempt at this goal was to modify some
Browning Machine Rifles to achieve this objective.The result of this was the M1922.The M1922 had a finned barrel to improve heat dissipation
a barrel mounted bipod, and a butt stock rest.
Some M1922’s had
the sling swivels moved to the side of the weapon so it could be
carried across the back of a mounted trooper.This weapon was sometime referred to as Browning Machine
Rifle like the original M1918.
While the M1922 gave mounted troops a readily portable automatic
weapon it did nothing to alter the need for frequent magazine
changes brought about by the parent weapon’s 20 round box
magazine design which remained unchanged.
In 1930 the Cavalry decided to try modifying some M1919 tank
guns with the 18 inch barrel to see if these weapons would be
more useful than the M1922.
The M1919 tank weapons came in two styles one having no sights
at all and one having a tube sight mounted on the left side of
the casing assembly.
The Cavalry test included jury rigging a front sight that was
mounted on the jacket near the muzzle and drilling a hole
parallel with the bore in the retracting knob for the top cover
latch.This made a
crude sort of rear peep sigh
This rear sight was close enough for early tests, but when the
Infantry got involved in 1931 it was decided to mount some sort
of windage and elevation adjustable rear sighting device similar
to the M1917’s.
Previous to WWI the Army had always mounted the rear sights of
rifles on the barrels just ahead of the receiver.
Wartime experience with the M1917 rifle, a U.S. Caliber.30
version of the British P14 Enfield turned out to be an eye
opening event, literally.
This rifle, manufactured By Winchester, Remington and a
Remington owned subsidiary Eddystone, so named because it was
located in Eddystone, PA, was adopted because Ordnance
could not produce enough M1903 rifles.
The M1917 rifle, commonly called an
had the rear sight
mounted at the back of the receiver.
Combat evaluations convinced the Army that the closer the rear
sight to the shooters eye the better the sight picture
especially when using a peep sight.
An additional benefit of receiver mounted rear sights on rifles
was that the sight radius was increased considerably.
The M1917 rifle’s rear sight wasn’t adjustable for windage, but
it proved to be a superior battle sight to the M1903’s finely
made, windage adjustable, target style rear sight.
The P14/M1917 rifle sight, protecting ears and all, was adapted
to the M1918 BAR which didn’t get a windage adjustable rear
sight until its M1918A2 makeover.
As things progressed on the modified tank gun testing on what
would later be known as
the M1919A2, it was decided to mount the rear sight on the top
cover latch placing the sight closer to the operators eye. This
required removing the retracting knob for the latch.
No matter, the sight base would act as a handle to pull the top
cover latch back.
Fig 1 Photo courtesy
of Jon Moran
This picture shows a M1919A2 commonly called the "Cavalry Model”
with its adjustable rear sight mounted on the top cover latch.The rear sight base serves as the retracting “handle” for
the top cover latch.
This assembly drawing, C64070, dated June 26, 1936 shows the
rear sight base attached to the cover latch.This arrangement was used not only on the M1919A2
but the developmental models of the A4.
It is difficult to read but Revision 1 dated 6-15-37 added
Major Items 51-83, the M1919A4 Fixed and 51-84 the M1919A4
Flexible to the "Drawing Pertains To" block in the upper right
This means that this rear sight base arrangement was intended
to be used on the M1919A4's until the adoption of the left side
plate mounted sight base was implemented.
When the left side plate mounted rear sight base was
adopted March 10, 1939, the latch mounted sight base "handle"
disappeared, and a new method of retracting the cover latch
had to be developed developed.
The period of time between official Ordnance Department
of the M1919A2, June, 1936 and the development of the M1919A4
a long way to explain why so few M1919A2’s were actually
Ordnance’s rebuild program, where M1917’s, M1919A2’s and
anything else laying around wereconverted to M1919A4’s explains
why so few, if any, M1919A2's survived in their original configuration.
This picture of a very early developmental M1919A4 Flexible
dated February 25, 1936 showing the rear sight mounted on the
the lack of a D35392 flanged bottom plate,
the slotted barrel
jacket for the 24 inch barrel, no cover hold open device and a
cotter pin style belt feed lever pivot.
This photo dated the same day as Fig. 3 shows a Fixed version
with a early style optical sight mounting that did not extend
over the top of the cover latch.
This may be the "telescopic" sight bracket that we have
not been able locate the drawings for.
The rear sight is still mounted on the cover latch.It is likely that this is the same weapon shown in Fig. 2
with the fixed style vertical buffer back plate installed, as
that is the only difference between the M1919A4 Fixed and
Figs. 3 and 4 are from a document titled “NOTES ON THE BROWNING
TANK MACHINE GUN, CAL. .30 M1919, E2, AND BROWNING MACHINE GUN
CAL. .30 M1919 A2 E3”
Courtesy of the Rock Island Arsenal Museum, Jodie Creen
pictures to the best of my knowledge have never been previously
As the design of the modified tank gun, now called the M1919A4,
developed provisions for optical sights were retained.In April of 1937 the RIA publication “Notes on the
Browning Machine Gun Cal. .30 M1919A4” shows the new C45965 rear
sight base mounted to the left side plate that would extend over
the top cover latch and serve a mount for the iron sights at the
same time retaining a mounting for optical sights.
This new style sight base combined the optical sight base with
the latch mounted sight base.
If you look at the left side of any production M1919A4 you will
notice that the rear sight base has a cut parallel to the bore
milled into the finished surface of the sight base along with 3
holes arranged in a triangular configuration.These holes are tapped ¼ X 28 threads per inch.
The tapped holes and milled cut served as a mounting for optical
optical sight modifications never went much beyond limited
experiential use but they were never eliminated either.
Since the new sight base carried the rear sight and its raised
protective enclosure there was no longer any way to retract the
top cover latch.
To remedy this problem a handle was developed with a grasping
protrusion on the right side that was to be riveted to the top
of the existing top cover latches to facilitate pulling back the
This is the original B150944 latch handle drawing. Note
that it has three mounting holes and and a slightly different
This drawing has no
authorizing signature and was intended to be used on the
s likely this drawing was only used to
produce prototype latches.
Drawing B150944 was completely revised on March 10, 1939 and
eliminated the "hump" on the left forward end of the latch and
one of the rivet holes and realigned the two remaining holes.
This re-design also required a piece mark imprint that was
removed by Revision 6, 6-18-42.
This drawing is the last version of the latch handle developed after the adoption of
the C45965 rear sight base that extended over the top cover
You will note that this drawing and the previous one are dated March 10, 1939 which is
the same date that the C45965 side plate mounted sight base uses
for an original drawing date.
There is also a note on this
drawing indicating that this part is not required on the
"alternative method of manufacture C93166 is used".
C93166 is the cast latch with the integral handle developed by
Saginaw Steering Gear which will be covered later in this
Top cover latches for both the M1917 and the M1919’s used a flat
spring that attached to the inside rear of the top of the latch
to apply forward pressure keeping the latch over the rear of the
Depending on the time frame the forward end of the latch spring
was either bent downward or had a “V” formed on the end.
This downward bend or “V” engaged a detent cut in the top plate and held the
latch in the forward position keeping the top cover securely
The dynamics of repetitive recoil forces require that the latch
be held firmly forward otherwise the top cover could spring open
during firing disabling the weapon.
New operators of the weapon invariably complain about the
difficulty of retracting the latch.
Even with a well lubricated latch it’s usually a two handed
Like most other things in life there is a reason why things are
the way they are, and why the latch is difficult to manipulate.
Photo Courtesy of Rollin Lofdahl
Left side, top and right side view of a cover latch with riveted
handle. The bead of weld was likely applied by the
Israelis to tighten the handle .
We have found no mention in any Ordnance publication of using
welding on any of the
caliber.30 Browning machine gun parts.
This illustration shows drawing 51-10-8 the M1917 top plate with the two
transverse milled cuts for the cover latch spring.
The left portion of the drawing shows the M1917 top cover latch
with the hole for mounting the spring retaining stud.This stud had a 1/8 inch diameter and the latch
spring just slipped over the stud.
This drawing also
has the latch knob hole and the knob itself. Notes show
that these parts are also required by "CL.51 DIV. 18" which is the
M1919 Tank Gun the predecessor of the M1919A4.
Other than latch knob hole this latch and top plate are
very similar to latches and plates used on the M1919A4.
Fig 7A Photo courtesy of Matt Danker
This picture is of two M1917 Westinghouse manufactured top
The upper latch has been Ordnance modified to the rivet on
The bottom latch and spring has been owner modified
to resemble the original stud mounted latch spring.
This illustrates the dilemma of trying to replicate a design
that was superseded over 70 years ago, one has to make or modify
This is detail D from drawing 51-10-34
showing the original design of the latch spring as used on
the M1917. It has the 1/8 inch hole to slip over the stud
riveted to the bottom of the cover latch.
It has been reported that some M1917
latches with the stud mounted springs have been observed
with the stud peened over to hold the spring in place.
It is not known whether this is some field
expedient method of attaching the spring developed by some
armorer with a little imagination, or something ordered by the
This is the letter prefix drawing B110372 Revision
18 showing the redesigned latch spring with the ¼ inch
hole that was used to rivet the spring to the cover latch.This drawing was not dated September 30 1936 which is the
date found on most M1919A4 production drawing probably because
this part was designed to replace the earlier design spring that
was adopted with the M1919A2.
Note the “Drg. Pertains To”area of the title block which lists the weapons this
spring is to be used on.
The M1917A1 is listed.
The M1919A4 is listed twice because the Fixed (51-83) and
Flexible (51-84) models have separate Major Item numbers.
The upper area of the drawing shows the "alternate" style of
fabrication with the hollow V.
This drawing produced by Saginaw Steering
Gear dated 3-2-42 and hand lettered "B110372" by RIA is what
caused the "alternate" design. Saginaw, ever trying to
improve the the weapon and cut cost and increase production, was
on their game as usual.
When pulling rearward on the latch you are flattening out the
is made so that when the spring is flattened the forward edge of
the latch clears the rear end of the top cover allowing the
top cover to be raised.
The back plate latch stop screw or the lug cast on the ArmaSteel
version of the back plate prevents the operator from pulling the
latch completely off the weapon.
“Bumping” the latch farther rearward with the back plate removed
causes the free end of the spring to jump clear of the forward
cut in the
top plate and the latch moves rearward about 2 inches farther
where the “V” on the end of the spring engages another,
shallower, detent cut milled in the top plate.
This second cut is a sort of “safety catch” to prevent the latch from being pulled off the top plate in one motion.
It is believed by this author that the “safety catch”
detent was to prevent
the loss of the latch and/or spring on early versions of the latch
assembly because the spring was not permanently attached to the
latch, it had the 1/8 inch hole that slipped over a stud on the
inside of the latch.
The transition from the stud mounted spring to the riveted on
version occurred after October 1, 1938 the original date of the
A152467 latch spring rivet drawing.
The May 1941 Standard Nomenclature List for the M1919A2 and
M1919A4 lists the latch spring as available in two styles, the
1/8 inch hole B17483 version for the A2 and 1/4 inch hole
B110372 for the A4.
The early latch spring was available
as a separate part until at least January 1944.
By 1947 only the latch ASSEMBLIES were available as
While the individual parts were listed,
they had no stock numbers shown and could not be ordered as
The primary reason for riveting the spring to the latch was, in
my opinion, an
attempt to “soldier proof” the weapon.
If the spring wasn’t lost removing the latch, sometimes during
reassembly the spring would become disengaged from the stud
jamming the latch on the top cover.
Freeing the latch invariably broke the spring or the
mounting stud rendering the
weapon useless unless someone held the latch forward while
This original drawing, D35393, from February 1938 shows the
“safety catch” cut on the left end of the Section A-A view.
This photo is of a Saginaw cast top plate with the two
transverse detent cuts.
Note the difference in the profile and depth of the "hold
close" detent on the right and the "safety catch" detent on the
The small letters "AC" on the rear sight windage knob indicate
that this knob was produced by the AC Spark Plug Division of GM.
The sight leaf itself is marked BA for Buffalo Arms Corporation.
Did AC supply parts to Buffalo Arms?
Hard to tell, as this sight leaf is a reworked Israeli 7.62X51
NATO sight and who knows if the sight was assembled
with the original knob after
The machining operation for the "safety catch" detent cut
was deleted by Revision 9 dated
August 27,1942, because with the latch spring now riveted to
the latch, the problem of lost or broken springs was greatly
The note in the upper left of the drawing now requires the
front half of the latch to be carbon case hardened probably to
prevent wear on the bottom of the plate and the area around the
cut where the cocking lever engages the top plate during the
recoil phase of the firing sequence.
Fig 9B Photo courtesy of Rollin Lofdahl
This photo shows both sides of a milled top plate with
both transverse detent cuts.
Note the wear area to the rear (left) of the where the
cocking lever dragged on the plate during bolt recoil.
The inside of the plate is marked "B 99" the meaning of
which is unknown.
The Ordnance Department didn't require marking on any of
the WWII era casing component parts other than the breech cam
lock, and after 1-19-42 the bottom plate.
owever, manufacturers were permitted to mark parts for
their own purposes with Ordnance Department approval.
Buffalo Arms marked many of their parts, likely to identify the
multitude of sub-contractors used to provide parts for their M1919A4
Photo courtesy of Carl B
Cast single groove top plate, note the pebbled surface in
the in the cocking lever opening. Saginaw's subsidiary
Saginaw Malleable Iron is the likely producer of this
Although we have not found the drawing mentioning the use
of malleable iron castings this top plate was likely produced
sometime after mid 1943. The half of the flaming bomb
stamp on the left side of the plate indicated that this was
installed on a Saginaw produced weapon.
Many cast parts have symbols or alpha-numeric codes that
were likely used to identify production the meaning of which is
not known because the Ordnance Department kept no records of
these manufacturers codes.
In early 1942 Saginaw developed the C93166 latch cast with an
handle which eliminated the riveted on handle.
Cast parts are fairly easy to identify as the un-machined
surfaces have a grainy or pebbled appearance.
This is but another example of Saginaw's ability to use the
ArmaSteel casting process to reduce the number of an assembly's
component parts, in this case from 6 parts on the Ordnance
designed latch to 3 parts on the cast latch, saving production
time for the parts no longer required, material and
the time required to assemble the parts.
The original date on this Saginaw produced drawing with
C93166 hand written on the face is illegible, however, the
Revision A date is 10-10-42 which is pretty close to the
original date of October 31, 1942 on the Ordnance drawing
It is possible that Saginaw was producing these cast
latches before these dates, but there is no way to know that.
C93166 Revision 4.
This drawing is the Ordnance drawing of Saginaw's cast latch.
The note at right center indicates that this design is an
"Alternative" design tor C64246, the machined latch, B150344 the
handle, and A159791 the rivets to hold the handle on.
The "Heat Treatment and Final Finish" block in the upper left
corner of the drawing shows "flame hardening" the 7 degree angle
on the lip of the latch that passes over the rear edge of the
cover to hold it closed.
Flame hardening for the cast
latch replaces carbon case hardening of the latching lip on the
machined C64246 latch, and is the standard method of heat
treatment for cast parts.
Alternate sometimes called Alternative designs indicated
that more than one design was approved, produced and used.
It is very possible that Saginaw was producing both type latches at the
From this point in time it is difficult to state which
manufactures other than Saginaw, the only known WWII producer of cast
parts for the M1919's, were using the cast latch, and since the
cast and machined latches were interchangeable there is no sure
way to know how weapons produced by RIA or Buffalo Arms left the
Eventually the latch assemblies using the flat spring was
replaced by a Saginaw Steering Gear designed latch featuring a
spring loaded plunger to hold the top cover latched and another
plunger at the rear to dismount the back plate assembly.
This plunger style latch was originally designed for the M1919A6
variant but proved so popular that it became the standard for
This Saginaw produced drawing is dated 8-12-43 and shows
the detail of the spring loaded plunger and the plug that kept
the top cover latched.
As of now we have not discovered exactly what prompted this
development. The date of this drawing is about two weeks
after the M1919A6 parts specific drawing are dated.
Since the A6 was originally used without a tripod in the
prone position this may have been an attempt to solve some
concerns regarding the difficulty of retracting the latch due to
the butt stock or it could have been developed because of
complaints about the latch being difficult to manipulate.
This is the original B7106949 plunger style latch assembly
drawing, dated October 7, 1943, showing that this latch is an
experimental part developed for the M1919A6.
Note that the Submitted and Approved signature areas are blank
meaning that this was not yet a part approved for production.
Revision 1 to B7106949 dated 3-9-44 has the authorizing
signatures and would indicate that this part was in production
at least by that date.
Originally this part was intended for the M1919A6 only.
However, Revision 3 dated 6-12-45 added the M1917A1, the M1919A4
Fixed and Flexible and the M1919A5 Fixed tank gun to the "Drg.
Pertains To" block.
By June 12, 1945 the war in Europe had been over for a month.
Fig 15A Photo courtesy of Rollin Lofdahl
Right side view of the plunger style latch assembly.
Fig 15B Photo courtesy of Rollin Lofdahl
Bottom view of plunger style latch assembly.
The way this assembly functioned was the vertical plunger, the
round part shown in Fig 15B
engaged the "
hold closed" detent cut in the top plate it was
spring loaded by the plug and the compressed spring held by the
horizontal plunger which was retained by the pin.
To remove the back plate the horizontal plunger was pushed
forward to clear the top edge of the back plate.
No more prying the latch forward with a screw driver wedged
between the back of the latch and and the back plate.
The note on the bottom left of the drawing in Fig 15 indicates that C64247 the latch
assembly for the A4's and A5 and C64280 the latch assembly for
the M1917A1 were no longer to be produced.
The older style latches remained in the supply pipeline and as
late as the April 1947 SNL still showed all four types.
The C64070 assembly with the sight base mounted on latch had no
associated stock number meaning it could no longer be ordered.
The C64247 assembly which was both the rivet on handle and the
cast style were classed as (usable) but the stock number was
hand lined out in my copy of the SNL.
This left the the B7106949 plunger style being the
preferred assembly, sort of.
The Army was not about to throw away perfectly good parts just
because it made the latch easier to manipulate.
This cut is from TB ORD 366 the Overhaul and Rebuild
Standards For Small Arms Material dated
It pretty much explains the required procedure in
subparagraph (g) The A4 and A5's could have either latch, the
M1917A1 could have either latch, and the M1919A6 got the plunger
style latch period.
Fast forward to 1969 and 1970 the TM9-1005-212-25 dated May 1969
shows only the plunger style latch for the A4 and A6, the M37
used an entirely top cover.
Depot Maintenance Work Requirements published in May, 1970 makes
no mention of the anything but the plunger style.
Like most things connected with the Ordnance Department, the
M1919's and WWII there is always a mystery.
Fig 17 Courtesy of the 90th Infantry Division Association
This is a picture from TM 9-206, the original M1919A6 Technical
Manual published in September, 1943.
The top cover latch shown does not resemble any thing we have
It appears to be some sort of flat spring that holds the top
Another anomaly in this picture is the use of the flat bottomed
grip, sometimes called the "short handle", C121054 cast back
plate normally used on the M1917A1.
This style grip lacks the cut out and spring clip used to latch
up the T & E mechanism when moving a weapon off the M2 tripod.
This picture was coded RA PD 79900 we believe this to be Raritan
Arsenal Publications Department #79900.
The Raritan Arsenal was located in Middlesex County, NJ
and among other things seems to have been the Ordnance Departments WWII publishing house.
This facility closed in 1963.
Many Ordnance publications are coded RA until about 1947 when
the U.S. Government Printing Office resumed publishing Ordnance
CREDITS AND ACKNOWLEDGEMENTS
Unless otherwise noted, all of the Ordnance
Department materials used in this article were provided by the
Rock Island Arsenal Museum.
A sincere thanks to the Museum staff and
especially Jodie Creen Wesemann for their help and assistance.
Without the cooperation of the Museum none
of these our articles would be possible.
As usual, Rollin Lofdahl and Matt D contributed photos of the real thing
which adds to the impact of the drawings.
Thanks to all who have contributed photos and provided