The air cooled ground type
Browning machine guns in caliber .30 are descendants of the Model of 1917 water
cooled “Heavy” by way of the M1919 air cooled tank guns.
Since they are related it
is not unexpected that many of the parts and assemblies are similar if not
identical.In this article we are
going to explore the various top cover designs and the associated attached parts
that make up the greater portion of the feed system of these iconic air cooled
While the 18 inch barreled
air cooled M1919 tank guns appeared in 1918 at the close of WWI the 24 inch
barreled ground mount version really dates from 1936.The M1919A4 and its variants owe their existence to Cavalry and Infantry
desires for an automatic weapon light enough to be man portable and quickly
deployed.Experiments to produce
this sort of weapon began in 1931 and continued until 1936 when the Army adopted
the design so familiar to the admirers of John Moses Browning’s genius.
The top cover allows access
to the feed way, extractor/ejector and even head spacing adjustments, and carries
the majority of the parts that advance the cartridges and hold them it in
position for extraction from the feed belt.
Over the service life of
the M1919 family many changes have taken place in parts design, materials,
manufacturing methods, and most importantly those changes improved the utility
of the weapon for the users.
The M1917 top covers had
the rear sight mounted on top of the cover while the production M1919 ground
weapons carried the rear sighting mechanism on a bracket mounted on the left
side plate.The M1917 had no
provision to hold the cover in an open position once it was unlatched and
raised.This deficiency was
remedied in production models of the M1917A1 and the M1919A4, A5 and A6.
Some writers believe the
changeover in 1938 to a cover that was held open at 45 and 90 degrees had
something to do with regard for the operator’s fingers getting pinched by a
falling cover. My personal belief is that the change to the cover hold open
feature was driven by a need to keep the cover open without someone holding it
with one hand during reloading or clearing jams.
There were two prescribed
methods of reloading, that is changing belts, in the M1919 the first required
the operator to stick the brass starter tab on the end of the cloth belt, or the
steel starter tab on the linked belt through the feed way on the left side of
the weapon pulling and releasing the bolt handle which placed a cartridge under
the extractor, the “half load”, then pulling and releasing the bolt handle again
to place a round in the chamber, the “full load”.
The other method, which was
the one likely most used, involved opening the top cover, raising the extractor
placing the first cartridge in the belt against the cartridge stops lowering the
extractor over the first cartridge, flipping the belt feed lever to the left so
that the lug on the bottom was positioned over the belt feed lever track on the
bolt top, closing and latching the top cover and pulling and releasing the bolt
Some cloth belts had
starter tabs on both ends, some on only end and the 100 round cloth belts used
in vehicles usually had no starter tabs at all, only brass grommets on either
One of the advantages of
using metallic links is that the belt can be made infinitely long by merely
removing the starter tab and a cartridge from the new belt and using the
de-linked cartridge to attach the new belt to the old.
M1 steel links were originally developed
in 1931. Their use in WWII was confined mostly to aircraft ammunition until very
late in the war when they started to appear in ammunition intended for armored
units.The use of cloth belts saved
precious steel and manufacturing capacity and continued well into the Korean
War.The Israeli’s used cloth
230 round 7.62X51 belts into the mid 1970’s.
While the second loading
method seems more time consuming, my bet is that most operators chose the open
the top cover route.
I have tried both methods,
albeit not under fire, and personally prefer opening the top cover.If someone was shooting at me, well, maybe I might adopt another policy
that didn’t require me to expose any more of my body to fire than necessary.
Top covers for the M1919
air cooled family fall into two basic categories, forged and finish machined and
cast and finish machined.
All of the production top
covers manufactured before 1943 were forged and machined.
While they were “covers“,
they were useless by themselves as they lacked the extractor cam and attaching
rivets, top cover extractor spring stud, and the latching “plate” and it‘s
attaching rivets.That’s eight
Saginaw Steering Gear,
Saginaw Malleable Iron and the industrial muscle and knowhow of General Motors
would change all that, forever.
Ordnance called user
replaceable grouping of parts related or attached to each other by either
necessity or manufacturing process an “ASSEMBLY”.
That’s how the SNL’s
(Standard Nomenclature List) showed the necessary stock numbers, that’s how you
ordered them and that’s how you got them.
SNL’s listed every part and
the quantity of that part need for one complete weapon along with tools and
However, many of the
component parts had no stock number listed in the SNL only the drawing/ part
number, in other words, while you could see the component parts and their
drawing numbers, you couldn’t order the replacement components, only the
assemblies or authorized parts.
ometimes the part capable
of being ordered and user replaced, like the original all steel barrel,
consisted of a single piece, other times the individual parts were combined into
a unit of issue like the extractor assembly. The reason for this is that field
users of the weapons had limited time and ability to effect repairs.
They were trained in
tactics, marksmanship, identifying basic operating problems and effecting
reasonable remedial action to clear stoppages and return the weapon to operating
The users had limited
access to tools, and no access to shop facilities like vices, welders, grinders
etc.They were not trained as
armorers, they were trained as operators of the weapon.
The average BMG hobbyist
likely knows more of the history, and internal workings of the weapons than the
combat users.The combat users had
much more important things on their minds, like staying alive.
Forging and machining to
final dimensions was the preeminent method of manufacturing firearms parts when
the M1917 was designed.The rough
forgings were oversize and the machining operations got the part to usable
produced high quality parts, it required skilled workman and properly designed
and maintained tooling to keep parts within working tolerances.
This method of fabricating
parts lead to a raft of parts interchangeability concerns which bedeviled Colt,
Remington and New England Westinghouse while they were manufacturing M1917’s
The upper illustration in
Fig. 1 is from SNL A-6 dated May 28, 1941 and the lower is from the same
document dated 6 September 1943 showing drawing numbers for the cover assembly
as well as all of the attached feed system parts.
After each of the parts, the cover
itself, the extractor cam, the latch plate and their attaching rivets and the
stud required to hold the forked end of the extractor top cover spring were
assembled they received an assembly drawing number of their own C9801.
None of the separate parts
of the feed system, the belt feed slide, belt feed lever, belt feed pawl, pins,
springs etc. were included, and they were ordered as separate parts.
This assembly drawing
number, C9801 was associated with, during WWII and until the adoption of Federal
Stock Numbers (FSN’s) in the ‘50’s, an Item Stock Number of A006 01 00340.
The A006 prefix indicated
that these parts were specific to the group A-6 which was the M1919 family.Some parts listed in the A-6 SNL carried a prefix of A005 this indicated
that these were also used on the M1917/M1917A1 which was a group A-5 weapon.
This is how the cover
assembly was packaged, inventoried and issued.If you needed a replacement top cover you ordered A006 01 00340 and what
came in the package would work, in spite of changes in materials, design, or
even the general appearance of the part.
This is not some strange
anomaly specific to the M1919’s but a general operational policy of the Ordnance
Department’s Field Services Division which was charged with the responsibility
of obtaining and furnishing both complete weapons and repair parts.
The M1919 family of weapons
along with nearly everything else Ordnance produced in WWII were in a constant
state of evolution.New parts appeared,
old parts disappeared, or were listed in the SNL’s as “used on guns of new
manufacture” for new parts or “used on guns of early manufacture” or just plain
“usable” for old style parts.
The upper Figure 1
illustration shows the original method of attaching the cover to the weapon.This method of attachment, a holdover from the M1917, was a simple hinge
pin, B17506, secured with a cotter pin, BFAX1CC, and had no hold open feature
for the cover.
Keep in mind that the cover
hold open feature was officially adopted for the M1919 in 1938 and this SNL was
published in 1941.This is pretty
typical for the SNL’s I have examined.The SNL’s sometimes lagged far behind new parts development.
This cut from ORD 9 SNL
A-6, the successor to the documents shown in Fig. 1, dated April, 1947 shows all
three M1919 top cover assemblies.All of them have the same assembly drawing number and stock number.
The first listing is the
“standard” cover; the second is “alternate A”. Both are forged and machined
assemblies consisting of eight parts.
The only difference between
the two is the two rivets that hold the extractor cam to the top cover.The only difference between the rivets is that the in the “standard”
cover the rivets are ground flat on the top of the cover while on the “alternate
A” assembly the rivets have domed heads, and are alternate parts themselves
(note the A suffix on the drawing numbers for the rivets).
This assembly drawing C9801
Revision 14 dated 6-12-45 shows the “standard” and the
“alternate A”, called out
on this drawing as “Alternative A” covers.Note the domed head alternate rivets holding the extractor cam and cover
spring stud to the top cover.
While author has never
observed an “alternate A” cover with domed head rivets no doubt there some out
there somewhere. And if any reader has one a picture would be appreciated.
The alternate A cover first
appeared as Revision 5 to C9801 dated 9-9-42 which is the same date as the
alternate dome rivets original drawing date.
The Saginaw ArmaSteel cast
cover is illustrated as “Alternative B”.
Many of the Ordnance
drawings and SNL’s reviewed have this alternative/alternate semantics duel.
There is also a note on
this drawing informing that the parts are only available as an authorized
“Alternate B” is, as you
can see, a whole different kettle of fish. Note that the drawing/part number is
a 7116476 number in Fig 2 indicating that this part is a new part for an
existing weapon or a new part for a new weapon while the assembly drawing C9801,
Fig 3 is common to all three variants because they are totally interchangeable
When, in late 1943, Ordnance started on
a program to make the drawing number, part number (piece mark), and stock numbers
common using 7 digit numbers with no Alpha characters they developed a
conversion system for the letter prefix series of drawings and reserved the
number range from 7000001 to 9999999 for new parts, even if some of these “new”
parts were interchangeable with older designs.
Alternate B is the Saginaw
designed and manufactured ArmaSteel cast cover. It consists of only two parts, the cover and the STUD, which is the
cover part that holds the forked end of the extractor top cover spring.
It is plainly evident from
a manufacturing standpoint that, all things being equal, an assembly consisting
of two parts is superior to one containing eight.
Not only that, but when you
figure in the time necessary to fabricate to tolerance EACH separate part, and
then assemble the parts to tolerance, the cast cover becomes even more
manufacturing techniques, like the ArmaSteel top cover, goes a long way to
explaining how Saginaw was able to reduce the contract price of a M1919 from
$657 in 1940 to less than $60 in 1945.
Saginaw Steering Gear had
been using perlitic malleable iron castings, which is what ArmaSteel is, to
produce difficult to machine auto parts prior to WWII, and as early as April,
1942 started suggesting to the Ordnance Department that these same casting
technologies could be adapted to machine gun parts production, saving steel,
machine time, and machine tools, increasing production, and saving money, all at
the same time.
Saginaw had never produced
a machine gun, or any other weapon for that matter, and approached weapons
manufacturing the same way they addressed their primary business which was
making interchangeable metal parts for the automotive industry.
They had no pre-conceived
notions about anything other than that they knew their business and they knew
that they were good at it.A little
self-confidence never hurt anything.
A latter day example would
be Gaston Glock, originally an Austrian manufacturer of household hardware, who
decided to enter a competition to produce a new sidearm for the Austrian
Herr Glock had no
experience producing firearms whatever.He also had no investment in tooling, reputation, or patents, and most
importantly, he carried no baggage from previously manufacturing firearms.
He made curtain rods, and
he started with a clean piece of paper.
That being said, he
produced what is now, arguably, the standard police sidearm in the US.
This remarkable drawing
dated 9-22-42, while a little hard to read, originated at Saginaw and was sent
to RIA.RIA, having no really good
way to index and catalog drawings produced by suppliers, had someone handwrite
“D7116476”, the Ordnance drawing number for the cast cover, on the drawing.It survived 67 years somehow getting microfilmed along with the other
“backfile” drawings.This Saginaw
drawing, or one like it, was likely used to prepare the Ordnance’s official
drawing which was dated August 10, 1944.
My personal opinion is that
Saginaw was producing cast covers well before the 1944 date, using their own
drawings which have the note to obtain any dimensions not on the Saginaw drawing
from Ordnance drawing D28106, however, there is no documentation that we have
uncovered as of yet that offers proof of this.
Drawing C9801 Revision 10,
the cover assembly, has a note on it mentioning drawing 7116476 as an alternate
This drawing Revision
shares the common date of August 10, 1944 with the original 7116476 drawing.
The first C9801 assembly
drawing that actually shows an illustration of the cast top cover is Revision 12
Saginaw titled this
drawing, as shown in Figure 4, “Machining Drawing of ArmaSteel Cover” and it’s
the first documentary evidence of a cast cover that our research has uncovered.The upper left area of this drawing shows the oval cut in the cover
necessary to allow a machine tool to cut the recess in the extractor cam to
allow the top cover extractor spring to latch in place.
On a forged cover with a
separate extractor cam this recess was cut into the cam before it was riveted to
The quickest way to
identify a cast cover, it’s the one on the left, is to look for the oval cut in
the cover seen near the latching area, in addition, the forged cover on the
right has the rectangular latch plate while the cast cover has the tapered lip
which is an integral part of the casting.
If you look closely at the
forged cover on the right you can see the lighter colored flat rivet heads of
the “standard” cover that attach the extractor cam and latching plate to the
cover. This difference in appearance is caused by the difference in steel types
and often shows up after Parkerizing.
The US furnished many
M1919’s to the Israeli Defense Force and the Israeli’s converted them from US
Caliber .30 to 7.62X51 NATO.These IDF converted weapons are the source of most of the “parts kits” being
Because of the differences
in the cartridge length and profile this conversion involved modifying the
covers and some of the feed system parts either by altering the parts themselves
or by designing and fabricating new components.
This photo, with the USGI
forged cover on the left and an Israeli modified cast cover on the right shows
how similar the covers are and a casual examination would miss the differences.
Part of the conversion
process to the ½ inch shorter 7.62X51 NATO round involved closing the feed way
opening by installing spacers and replacing the original rear cartridge stop
with one of a different design.This required changes in the belt feed pawl, cover and the belt feed slide which
can be seen in Figure 6.
In this photo the Israeli
modified cast cover is on the left and the “dog leg” arm, which prevents double
feeding if the extractor fails to withdraw a cartridge from feed belt, on the
belt feed pawl is plainly visible as are the differences in the belt feed slide
and the clearance cut in the cover itself required by this redesigned/modified
Most if not all IDF
modified covers have a squared off “U” symbol stamped on the top and bottom of
the cover in the hinge area.This
is a Hebrew symbol for “Peace through strength” and serves the same purpose as
the US “Flaming Bomb” ordnance symbol.
Some IDF modified covers
have a label affixed to the cover.
The modified belt feed
slides are similarly IDF marked on the top, visible when the slide is extended
to the left.The mark on the cover
itself has been almost obliterated.
This IDF modified cast
cover is used on a Caliber .30 Ohio Ordnance Works semi-auto M1919A4/A6 with the
USGI rear cartridge stop installed and functions perfectly.
Note the oval cut and the
extractor top cover spring visible thru the opening.
Also note the “dimple” to
the left (rear) of the belt feed lever pivot bushing nut and the old stake marks
on the cover to hold the nut in place and the stake marks on the nut to hold the
pivot pin retaining cap screw.Later in this discussion we will revisit the belt feed pivot parts which could
make up an article in themselves.
Additionally, the IDF
modified some of their belt feeds levers and pivot pin assemblies to one of
their own design.
Photo courtesy of Carl B
This top cover likely started out as a cover for a M1917
water cooled either having the sight base removed or having the
two rivet holes to the left of the top cover extractor spring
stud and the single hole to the left of the latch plate rivets
filled before the sight base was installed.
Several of these have been observed with the Springfield
Armory "eagle head" inspection stamp on the edge of the right
feed way opening. At some point it was remanufactured into
a cover for use on one of the M1919 models. Some also have
WWI era New England Westinghouse W in a a circle manufacturer's
markings. It is possible these remanufactured covers could
also be Colt or Remington marked. It is difficult to say
who did the remanufacturing, Springfield Armory would be the
Photo courtesy of Carl B
Springfield Armory inspection stamp and "P" proof mark.
Fig 7A Photo courtesy of
The IDF took a standard
USGI belt feed lever and modified the pivot pin hole to accept a tapered pin
inserted from the bottom which extended up through the bushing and bushing nut
and was held in place by a cotter pin resting on top of the modified bushing
Obviously the original
pivot pin, cap (set) screw and toothed washer were not required with this
This arrangement kept the
belt feed lever from ‘drooping” due to a worn pivot pin or a worn hole in the
belt feed lever itself.
The IDF did not usually remove the
US piece marks imprinted on the belt feed lever.
Exercise caution when
purchasing belt feed levers.
Fig 7B Photo courtesy of
Another style of IDF
modified top cover note the milled out area to accommodate the folded adjustable
front sight when the cover is raised to the 90 degree position. This cover
is equipped with the IDF designed cotter pin
pivot retaining system.
This is the forged standard
style previously shown in Figure 3.
This belt feed lever retaining system using
a cotter pin is reminiscent of the pre war US cotter pin style and would be the
one used with the modified feed lever and the tapered pivot pin shown in Fig 7A.
Silvan Arber photo
The milled slot in the top cover is a U.S. modification. The first record
of this that we have discovered is in the Depot Maintenance Work Requirements
dated April 1970 but this modification likely dates from much earlier as
witnessed by this photo of a RIA produced M1919A6 likely
produced in the first half of 1955. It equipped with the
early type of adjustable front sight and the milled slot.
The style front sight was designed in May of 1946 but the
Modification Work Order to replace the fixed front sight didn't
appear until October 1952.
This is drawing 6528106
Revision 22 dated 10-7-48 is the forged top cover.This drawing has a note that advised “Was D28106”.The original D28106 drawing produced by Springfield Armory is dated June
1, 1931.It is a redrawing of the
letter prefix and 7 digit renumbering of drawing 51-18-12 for the top cover of a
M1919 tank machine gun the weapon that the M1919A4 developed from.Most M1919A4 production drawings carry a June 30, 1936 original date.
This drawing carries a June
31, 1931 date because the tank gun drawing was converted to a letter prefix
drawing prior to the development of the M1919A4.
Note the rectangular cuts
on the pivot pin bushing hole and the dimple to the rear of the hole.These features date from the original drawings for the M1917 and would be
part of the drawings for M1919’s until eliminated on Revision 23 dated 12-6-49,
12 years after they were made obsolete due to changes in the pivot pin assembly
This 12 year time lag maybe
the result of the availability of the original spring type pivot pin assembly at
least until January, 1944.
At the beginning of this
article Fig 1 showed the parts that attached the top cover to the casing. In the
spring of 1937 the Rock Island Arsenal now in charge of all Caliber .30 ground
Browning machine gun production published a document titled “Notes on the
Browning Machine Gun Caliber .30 M1919A4” this 22 page illustrated booklet
covered the changes necessary to convert the excess M1917 water cooled weapons
left over from WWI to the air cooled M1919A4.
Before this original
“Notes” document was published, it appears that the original spring type belt
feed pivot pin used on the M1917 and early M1919A2 and A2E3 was changed to one
similar to the Major Item 51-24 Browning Aircraft MG. M18 and Major Item 51-25
/M19 aircraft BMG pivot pin assembly.This assembly had the headless pivot pin inserted from the top of the
cover through bushing nut, bushing and belt feed lever and was held in place by
a cotter pin.
We say this because the
original A157434 pin lacked a head and only had 1 transverse hole
Without a cotter pin
passing through some sort of retainer, the pin would fall out it the weapon was
The original “Notes” also
changed the belt feed pivot assembly to one where the pivot pin
now with a head, and with the same
drawing number A157434 but Revision 2, was inserted from the top of the cover
through new style bushing nut, bushing and through the belt feed lever.This style pivot pin was held in place by a spring steel cap that snapped
over the modified bushing nut.
These early conversion
instructions retained the cover hinge pin with no hold open feature but added a
bracket to the left side plate which held the rear sight which was removed from
the cover latch.
By spring 1938 RIA
published an addendum to the original “Notes” called
“Notes… Modified” which included the
hold open feature consisting of a spring loaded fixed and a movable plate with
bolt and castellated (castle) nut secured with a cotter pin and a slightly
altered belt feed lever as shown on the lower half of Fig 1.
This same publication also
outlined some changes designed to raise the firing rate of the M1919A4 to 600
rounds per minute by using a muzzle (booster) plug with a .617 opening and a
redesigned driving spring made with .047 diameter wire.
These changes designed to
increase the firing rate were not implemented on production weapons.
Photo courtesy of Rollin
This photo shows side view
of reproduction spring style belt feed lever pivot pin.
I refer to this style pin
as “type 1”.
This pin was inserted
through the top of the cover and the belt feed lever and the rectangular
shoulders on the pin passed through the corresponding cuts in the cover.The pin was rotated clockwise and the spring (arm) was locked in place
when the protrusion on the underside of the spring engaged the dimple in the top
The 1941 SNL lists this
style of pivot pin with an assembly drawing of A135054 as “used on guns of early
manufacture M1919A2, M1919A4”.
A similar pin design was
used by Browning to lock the trigger group and the gas tube assembly to the
It appears that during
development of the A4 that this spring style pin arrangement was replaced by the BMG aircraft
type cotter pin retained pivot assembly.The cotter pin style did not remain a standard for long.
This cut from the 1940 FM
23-45 courtesy of the 1919a4.com forum and James Jones shows the cotter pin
retained pivot pin that I call “type 2”.
The picture above was taken by the author at and through
the courtesy of the RIA Museum and shows the cotter pin style pivot pin assembly
on a M1919 Aircraft BMG marked T1-1.
The only text mention of
this style found so far is in a narrative in SNL A-6 dated May 28, 1941, page 52
which describes the cotter pin type 2 style noting that the pivot pin is
changeable form the top.It also
describes the type 3 “snap cap” assembly as being used on the “further modified”
This SNL narrative also
describes the original M1919A4 as “mainly used as armament for combat vehicles”.
This illustration from the
1937 “Notes” document shows the next advancement in pivot pin assembly design
which I refer to as type 3. The 1941 SNL
shows this design with an assembly drawing number of B147304 “M1919A4 used on
guns of new manufacture”.Most of
the parts are recognizable with the exception of 7 which is the spring steel cap
that holds the pivot pin in place.I stared at this for some time trying to figure out what it was and how it fit
on the assembly, at the time I was not in possession of the drawing of the cap.
Finally I called Rollin
Lofdahl who had actually seen one of these and he explained that it was like a
bottle cap and snapped over the bushing nut (5 in this drawing) holding the
pivot pin in place and in turn the cap was held by the recess shown by 6.
The four holes near the
bottom of the bushing nut allowed the nut to be tightened using a pin inserted
into one of the holes.
The next figure is the
drawing used to produce the cap which makes things much clearer.
This is the cap that holds
the pivot pin in place on what I call the type 3 pivot pin assembly.
Fig 11A.Photo courtesy of Theo Servetas, Aberdeen Proving Ground, June 2009
This photo shows a snap cap
type 3 pivot pin retaining system assembled on a forged top cover on a M1919A4
displayed at Aberdeen Proving Ground.It is likely that the only extant pivot pin assemblies like this are
either on museum display or have been recreated by hobbyists building “period”
The plaque accompanying
this weapon described it as “c. 1942” M1919A4 which it is.
This is another Saginaw
produced drawing dated 6-5-40 which Jodie Wesemann discovered while copying some
B17503 belt feed lever drawings.
Why this drawing was hand
numbered with the belt feed lever drawing number is unknown.
This drawing goes a long
way to explaining why the “type 3” snap cap pivot pin retention system went
away.The 6-5-40 date was before
Saginaw got its first production contract to produce M1919’s and about the time
when the “Educational Contract” was winding down.
From the notes on this
sketch it appears that problems developed when the top cover was closed with the
operating lug on the belt feed lever not over the track in the top of the bolt.
noticed, likely during function firing that after the third of fourth time the
cover was closed in this manner the pivot pin was pushed upward with enough
force to pop off the spring steel retaining cap. Eventually, during firing, the
pin could walk its way upward enough the belt feed lever would fall off the
Obviously after the lever
fell off the pivot pin the belt would not advance, and depending on how it was
positioned when it fell off, the lever lying on top of the bolt could cause
serious damage when the weapon fired the last cartridge chambered.
Back to the drawing board.Literally.
We, as of yet, have not
discovered what transpired when Saginaw’s sketch arrived at RIA but by July 18,
1941 the final pivot pin bushing nut, drawing A196284 that retained the pin with
the cap screw and the new pivot pin assembly B110529 containing that nut both
SNL A-6 Changes No. 2 dated
January 30, 1942 notified the field forces that a new pivot pin assembly,
drawing number to B110529, which is the one we are most familiar with was
available.This assembly lasted
until the end of the service life of the M1919 ground guns.
Changes No. 2 also changed the drawing
number of the bushing nut from A157433, the one shown in Fig 10 to A196284, the
style that accepted the cap screw to retain the pivot pin, illustrated on the
bottom of Fig 1.
The September 1943 SNL no
longer shows this “snap cap” type 3 assembly but continues to list the original
spring style pivot pin as an available part along with the assembly B110529
which is shown on the lower part of Fig 1.
The spring pivot pin
assembly, type 1, A135054, and the cap screw B110529 style, which I call type 4,
are shown with A005 stock number prefixes which indicate that they were also
intended for use on the M1917/M1917A1.
None of the bushing/nut
style pivot pin assemblies require the rectangular cuts in the pivot pin hole
shown in the cover in Fig 8.
This pretty much covers the
pivot pin assemblies, the only changes made after adopting the B110259 last
style assembly was the addition, sometime after 1949, of an additional internal
toothed washer between the top of the cover and the bottom of the pivot pin
bushing nut.This can be seen on
the forged cover on the right in Figure 5.My thought is that the toothed washers were substituted for staking the
components in place.
TB ORD 366 issued in August 1949
contains rebuild standards for the M1919’s and other weapons; specific mention
is made that the B110259 pivot pin assemblies are the only approved parts.
There is no mention of the toothed
washer between the bushing nut and the top cover.
This would lead me to believe that there
might have been some weapons equipped with older spring style on the loose.In any event, any weapon undergoing arsenal rebuilds should have had the
older style assemblies replaced. This directive also covered M1917A1’s.
Originally, the M1919A4
Fixed BMG was intended use in the M2 and later the M3 Stuart tank; it was
nothing more than an A4 Flexible equipped with a horizontal buffer back plate
having no pistol grip.
In May of 1942 the M1919A5
Fixed BMG, Major Item number 51-114, was introduced into the Ordnance system.
As tank development
proceeded it became apparent that there was a need for a different fixed type
M1919 for coaxial mounting in a tank turret. In May of 1942 the M3A1 version
Stuart light tank appeared and the M1919A4 Fixed, previously used coaxially with
the M23 37mm main gun was replaced by the M1919A5.
In a coaxial mounting in a tank the
machine gun is trained and elevated with the same mechanism as the main gun.
Because of space
limitations these mountings required a method of bolt retraction not requiring
the operator to reach forward and operate the conventional bolt handle it also
needed neither front nor rear sights, or a pistol grip.
The same tight quarters
also required a different style of hold open feature for the top cover and a
different type of latch tensioning mechanism which is shown in Fig 12.
fixed/movable hold open plates and the tensioning spring, hinge bolt and
replacing the bolt handle with a cocking stud gave additional right side
clearance and the bolt retracting handle allowed the bolt to be operated from
During the 1950-1954 time
frames some M1919A4 Fixed and Flexible guns were altered by the Rock Island
Arsenal to an A5 style configuration and became known as M1919A4E1.
These weapons were modified
to satisfy a requirement for fixed type weapons for coaxial mounting in tanks
while the M37 was being developed.
The M37, the last of the
breed, eventually replaced the A4 Fixed, the A5 and the A4E1’s it could be fed
from either right or left and used a completely different top cover design.
Many of the M37 parts were
not interchangeable with the M1919’s.
The M1919A5 design specific
drawings were dated May 23, 1942, however, the first illustration that we could
find of the A5 appearing in an SNL were from the ORD 9 SNL A-6 dated April of
1947 pictured above in Fig 12. The
lower portion of Fig 12 shows the completely different hold open device
officially referred to as a “Detent, cover group assembly (M1919A5)”.
This assembly drawing was
B195941 however no stock number was listed in the 1947 SNL.
There may be earlier
versions of an SNL showing the M1919A5, but I haven’t discovered any as yet.
One of the problems most
people encounter when doing research on Ordnance publications, drawings, and
other documents is a lack of understanding how the system worked.
Drawing numbers in the
letter prefix system, adopted in 1922, which mandated, among other things, that
only one part could be depicted on each drawing were assigned in a sequential
order for each letter size.There
was no readily observable connection between the drawing number and the weapon
or weapons the part was used on.
However if you looked at
the drawing itself there was a “Drawing Pertains To” block which listed each
weapon the part was used on and , if it was part of an “assembly”, what the
assembly drawing number was.
Conversely, you could go to
the Class and Division drawings and find a list of the drawings for each part
needed for that item along with illustrations showing where parts went on the
The letter indicated the
size of the paper or other medium the part was drawn or traced on.
As you progressed up the
alphabet from A through E the drawing size increased.
This system allowed a part
common with several weapons to have a single drawing number.
Each drawing displayed the
piece mark (part number) for each part.Just because each part had a piece mark does not mean that part was so
marked.The drawing of the part
would indicate whether or not the part should be marked and where.Sometimes there was a “drawing” which was not a drawing at all but a
table listing which parts of which weapon were required to be marked and how.For the M1919A4 this “drawing” was B169913.
The term “revision” to a
drawing is equally misunderstood.Revisions are changes to the drawing, not necessarily to the part.As a matter of fact, the majority of revisions have nothing to do with
the design of the part.
Equally important to
remember is that not every revision to the drawing resulted in a change to the
required piece mark.
The drawing shown in Figure
13 had 11 revisions but only revision 2 changed the required piecemark; however,
none of the revisions affected the interchangeability of the part.
Most revisions are
administrative in nature, sometimes adding either weapons or assemblies to the
list of what the part pertains to, adding information about the previous history
of the drawing, or adding information about what the drawing became.
This is drawing A157434
Revision 11 of the pivot pin.Each
revision has a date and the circles with numbers and the leaders (arrows)
pointing to what was changed by each revision.Revisions 3, 6 and 10 added weapons to the “Dwg Pertains To” block and
Revision 5 added the belt feed lever pivot assembly.
Revision 1 actually changed
the complete design of the pin and Revision 2 altered some dimensions and added
“-2” to the piece mark shown to the right of PIVOT, BELT FEED LEVER with the
letter prefix of the drawing number almost enclosed by a large “C”.The piecemark was not imprinted on the part.
At the very bottom of the
drawing there is the note that converted this letter prefix drawing to the 7
digit format on 5-10-48 WO/C (without change).
The original date of this
drawing is September 30, 1936 which is consistent with the majority of drawings
specific to the production M1919A4’s.
The scale of this drawing
is 2/1 which means the part on the drawing was drawn twice the size of the
A size drawings are 8 ½ X14
inches, today’s “legal size” and are the smallest.
This is the original drawing of the pivot pin, type 2, designed to be retained
by the cotter pin.Both drawings
have the same drawing number but this one dates from Jan 22, 1936.
The reason that the drawing numbers have not changed is that this pin COULD be
used in lieu of the pin in Figure 13 IF you had a cotter pin and the necessary
parts to retain the pivot pin.
Ordnance was supposed to change the drawing numbers only when the parts lost
full interchangeability even though the parts looked nothing alike.
is not likely that this style of pivot pin was used on many if any production
This pin was part of the evolutionary process that developed the standard for
the production weapons.
Remember the example of the previously mentioned “Changes No 2” to the 1941 SNL
which changed the assembly number for the belt feed pivot assembly AND the
drawing number for the nut.Why?Because these items were not interchangeable with the previous
part/assembly even though the other parts of the assembly remained unchanged.
Generally parts of weapons where the drawing numbers remained consistent never
altered the design enough to compromise their interchangeability even though the
piecemark was changed by a revision suffix.
SNL’s usually did not include revision numbers when showing parts or assemblies.
There were several reasons for this.
Adding revision numbers took more space and would generate confusion about the
drawing/part number and issues would arise relating to whether or not a part
with a lower revision number was usable.
While the revision numbers were vitally important to the manufacturers of the
part, as long as the drawing number of the part or assembly provided agreed with
SNL listing, the revision number was immaterial to the field services because
the part was fully interchangeable.
The only persons who presently have an interest in revision numbers are
researchers and hobbyists who are attempting to date parts, understand the
evolution of the weapon design or to return a weapon to “correct” condition.
Herein lays a very large problem.
Even if you had a brand new weapon in the original, unopened packaging there is
no guarantee that all of the parts would be “correct”.
When weapons were assembled at the factory any usable parts or assemblies on
hand were pressed into service.
While parts with revision numbers could not have been used prior to their
revision dates, because they didn’t exist, older parts on hand could have been
The belt feed slide, belt feed pawl and spring, and the spring pin used to
attach these parts to the cover along with the extractor top cover spring and
the M1919A4 cover hold open parts drawing numbers remained constant up to the 7
digit conversion in 1948 and then on to the end of their service life.
This does not mean that changes did not occur to the parts, it means that the
design of these parts never changed enough that they lost their
Some revisions merely altered tolerances by .001 or .002 + or -.Revisions like these would be nearly impossible to detect even if you
measured the parts.
a part had lost its interchangeability it would have been given new drawing
number, piecemark and stock number.
Depending on the particular weapon, when undergoing arsenal rebuild, revision
numbers of parts took on great significance.
Arsenals or other rebuild facilities had the resources to identify earlier
design parts that required replacement even if they did not have piece marks to
good example of this would be the arsenal rebuilds of M1919’s post WWII.
the end of WWII production of the M1919 the original cover extractor spring
stud, drawing number A24604, that held the forked end of the top cover extractor
spring in place was redesigned and superseded.
This redesign of the stud, shown on drawing A7123315 with an original date of
May 25, 1945, increased the clearance between the inside of the top cover and
the head of the stud to .160 inches from the original .155 dimension.The reason for this change is presently unknown.
This change may have had something to do with the design of the top cover
extractor spring, originally .05 inches thick made of ‘forged steel” vs. the
last drawing 6517513 showing 18 US gage spring steel (.0478 inches thick)
however, this spring’s design never changed enough to effect its
interchangeability and warrant a change to its drawing number other than the
conversion to the 7 digit system which never altered the design of the part at
The late design spring was thinner than the earlier design but made of different
Why a thinner spring would require greater clearance is unknown, perhaps it just
made the spring easier to install or possibly altered the force applied to the
The people doing these arsenal rebuilds were assembly line workers, taught to do
one or two functions they were not “armorers” who knew the entire weapon.
The studs are not interchangeable because the new part has a new drawing number.
The new part also has a new stock number listed in the 1947 SNL.
ORD 366 the rebuild standard for small arms issued in 1949 calls for the
replacement of the older style stud.
Obviously, it would be impossible to detect the difference of .005 just by
looking and the stud was not piece marked.
The arsenal rebuild facilities most likely made a “no-go” gauge to check the
head clearance and determine which, likely all of the studs because of the
lateness of the new part drawing date, required replacement.
Weapons that did not get arsenal rebuilds soldiered on with the earlier stud.
The making of gauges, fixtures, jigs and special purpose tools used in the
manufacture, assembly and rebuilding of weapons was a large part of the process.Some of these special purpose items had letter prefix drawings and some
were identified by a special tool room system of numbering drawings.
The last item on the list of top cover feed parts that we are going to discuss
is the belt feed lever.
The first listed M1919A4 belt feed lever, B144825 did not share the drawing
number with the original M1917 belt feed lever shown
on drawing 51-10-18D which had a letter prefix conversion drawing number of
C8460 dated June 1, 1931. This is the original date common with the majority of
M1917 drawing conversions to the letter prefix system.
There are only two C8460 drawings available and they carry a note at the bottom
“For future manufacture use B-17503”.
would appear that while there was a C8460 drawing it was not used to produce any
belt feed levers.It unknown why
Ordnance even bothered to produce the C8460 drawing in 1931, unless it was done
in error, since they already had a B17503 drawing dating from 1924.
The operating lug on this drawing, 51-10-18D/ C8460, is .446 (-003) long.
The earliest B144825 drawing is dated January 23, 1936 and it appears to be a
nearly exact copy of the C8460 but has no authorizing signatures it also has a
B144825 next appears on September 30, 1936 this time with authorizing signatures
and a date common with most of the M1919A4 drawings it has a lug length of ,446
B144825 Revision 1, 3-10-39, changes the lug length to .510 (-005)
The earliest B17503 drawing available is dated April 4, 1927 and is a Colt’s
Patent Firearms drawing endorsed by the signature of Ordnance officers at the
Springfield Armory. This drawing was
revised on 1-31-36 to add a note qualifying the tolerances allowed to the part
not otherwise shown on the drawing, and to add Major Item 51-77 the M1919A2 to
the list of weapons this drawing pertained to.This drawing showed a lug length of .520
Other weapons listed in the “Drawing Pertains To” block on the Colt’s drawing
were the M1917, M1919 Tank Gun, M1919 Aircraft gun, and the “M18M1” also an
Plate A in the RIA Notes…Modified document dated March, 1938 shows the B17503
belt feed lever as the type lever used on the modified M1919A4 gun.All of the dimensions shown on Plate A agree completely with Revision 1
of the same numbered drawing that originated at Colt’s.
Revision 2 to B17503 dated 2-1-38 redrew the drawing at RIA and removed the
reference to Colt’s.
B17503 Revision 3 dated 5-27-39 added the M1919A4 Fixed and Flexible and
shortened the operating lug to .468 (-.005)
During the evolution of the M1919A4 several designs of belt feed levers were
developed; the earliest was the B144825 Revision 1 with the .510 lug. Followed
by the B17503 which was designed, apparently, for both the M1917 and the M1919
family with the .520 lug and ending up with a .468 (-.005) dimensioned lug shown
on B17503 Revision 19, 12-27-45
Even though the B144825 lever design was superseded by the B17503 lever with a
shorter lug dating from 5-27-39 it was classed as “useable” through the 1944
The B144825 lever had a stock number with an A006 prefix indicating that it was
for the A4 only while the B17503 had an A005 prefix indicating it would also fit
Ordnance, in one of their “Houdini” acts, on 5-27-39 by Revision 2 to B17503
shortened the .520 operating lug to .468 and did away with drawing and belt feed
lever B144825 because both parts were functionally identical even though the
B144825 had the .510 lug.
The last of the belt feed lever drawings for the WWII period is (B) 6017503
Revision 20 dated 5-10-48 which is the drawing that redrew B17503 including all
the previous revisions and converting the drawing to the 7 digit format.This drawing also changed the piecemark, now called a part number, to 6017503
and finalized the lug length at .468.
suspect they kept the B17503 drawing number because this number now appeared in
all the publications for the M1917’s.Switching the drawing around avoided reprinting many documents and
revising the M1917 drawings.
This is another case much like the drawing number/parts swap that occurred with
the M1919 slotted/holes barrel jackets.
any event, the operating lug remained nearly the same .468 length except that
its tolerances changed along with the dimension called out on the drawing.
The end result was that different drawing revisions expressed the lug length in
different ways but it was about the same length from about May 1939 to the end
of its service life.
elt feed levers were the only part in the top cover and its attached components
that was required to be piece marked starting with B144825 in September of 1936
which was marked B144825 and likely marked with the producers identification.
The Colt’s drawing B17503 Revision 1 dated April 4, 1927 changed the piecemark
to B17503-1 but there were no instructions to imprint the part.
marks on belt feed levers are believed to be:
B144825 (likely very rare) there was a Revision 1 to this drawing, but it did
not change the piecemark.
B17503-3, beginning 5-27-39
B17503-4, beginning 3-29-40
B17503-6, beginning 4-18-41
B17503-14, beginning 8-14-43
The B17503-14 and subsequent belt feed levers featured a slightly thicker (.010)
lever except for the 1.25 inches on the end of the lever that fit into the belt
feed slide.Regardless of this
minor change, the reason for which is unknown, all of the B17503 levers are
6017503, beginning 5-10-48
All of these should have various manufacturers’ codes imprinted on the lever.The prescribed location for this piece mark was on the top (cover side) of
the lever and on the operating lug end in 1/16 inch characters.
have a RIA B17503-3 lever marked on the bottom side so even they didn’t always
follow their own rules.
The March 1938 “Notes Modified” publication illustrated belt feed lever B17503
shown below from Plate A.
The text from “Notes… Modified” describes the change as lengthening the
operating lug to .520 inches.
The “operating lug” is the stud that travels in the serpentine track in the top
of the bolt.
The original M1917 belt feed lever had a lug length of .446.
Drawing B17503 went through 19 revisions before the 5-10-48 renumbering
(Revision 20) when it became (B) 6017503. It was authorized to be used in both
the M1917A1 and all of the M1919’s
the renumbering process B size drawings had 6,000,000 added to the original
There is an RIA pamphlet, and some authors including myself, that have described
this B size renumbering process as “adding the numbers 60” to the original
This is somewhat misleading.
All drawings were supposed to end up with 7 digits and while adding 60 to the
original drawing number in the case of the belt feed lever produces a seven
digit number if the original drawing had contained only four digits adding 60
would only produce a 6 digit number.
the original B size drawing contained 6 digits like B224849, a part of M1919A6
butt stock, and you added 60 to that you would end up with an 8 digit drawing
Even though the 1943 Ordnance plan to have a common drawing, part and stock
number containing no alpha characters was implemented, and every drawing was
redrawn/renumbered, the practice of including the letter size continued because
that’s the first step in locating the drawing because that’s how the drawings
All the A size filed in one cabinet all the B size in another, and so on.
addition, as we have seen in the previous example, not all B size drawings would
start with 60, the A6 butt stock part/drawing/stock number became 6224849.
The drawing letter size in 7 digit conversions was usually placed in a box
adjacent to but separate from the drawing number.
The belt feed lever is another example of a large number of revisions to a part
drawing which didn’t have any effect on interchangeability, even though the belt
feed lever was required to be imprinted with the current piece mark.
addition the B144825 belt feed lever continued to be “useable” until the supply
was eventually exhausted even though the B17503 lever was the only lever to
appear on the B169913 drawing dated 4-7-42 listing all of the parts of the
M1919’s required to be marked.
was “useable” because it was for all practical purposes the same part with a
This Saginaw drawing, another of Jodie’s finds, from May of 1942 which they
numbered B-17503 in their title block and someone at RIA handwrote B17503 shows
an experimental belt feed lever featuring a slight offset bend on the end of the
lever that operates the belt feed slide.
also slightly lowered the height of the upper pivot bearing area and lengthened
by the same amount, approximately .020 inches, the operating lug.
does not appear that this design ever went anywhere.
This and the previous Saginaw drawings, most likely, have never been published
This drawing which appears to have originated at Springfield Armory shows a
“modification” to the B17503 design that features a roller on the operating lug
of the belt feed lever.
Section AA shows the lug end of the belt feed lever with a shaft for the roller
and a hole through the lug for the rivet needed to secure the roller onto the
lever.The roller is shown right of
center and the entire assembly to the left of center.Because of the poor quality of the microfilm we have been unable
determine a date when this was proposed.
The drawing is a non-standard size and was microfilmed in two pieces.It is likely that this drawing was transferred to the Rock Island Arsenal
from the Springfield Armory along with all of the other Caliber .30 BMG
documents when RIA assumed responsibility for production of these weapons.
Like the Saginaw proposed belt feed lever shown in Figure 16 there is no
evidence that this design ever went beyond the drawing stage.
These last two drawings give us a unique look at what was going on behind the
This concludes our discussion of the top covers and their associated feed system
Additional articles describing the M191A4 design history will be forthcoming,
hope the reader has found our efforts both entertaining and informative.
As always, comments are welcome.
usual, I have had a lot of help with the research; however I am solely
responsible for the content, if there are errors or misstatements I bear the
CREDITS AND ACKNOWLEDGEMENTS
Rock Island Arsenal Museum, Jodie
Creen Wesemann who supplied all of the ordnance drawings and publications
featured or quoted in this article.
Jo is one of those rare persons with
an instinct for the important.The
Saginaw Steering Gear produced drawings and the “roller lug” Springfield Armory
drawings were not requested by the author but Jo included them because she
sensed that they were unique, and as usual she was correct.
Without the Museum’s cooperation
none of the things displayed here would be possible.
Thanks to my good friend and an
important contributor Rollin Lofdahl who is always there to help in deciphering
all of this information.
Thanks to all those members of the 1919a4.com and beltfedshooters.com forums who
have helped with pictures and comments, and for sharing the really odd finds
that crop up now and again.
And a special thanks to Jon Moran from the Browning Machine Gun site.
Photos are individually credited; those lacking a credit are the author’s.
The Browning Machine Gun Vol. 1, Dolf L. Goldsmith Collector Grade Publications, INC
Hard Rain, History of the Browning Machine Guns, Frank Iannamico Moose Lake Publishing, LLC
U.S. Infantry Weapons of WWII, Bruce N. Canfield Andrew Mowbray Publishers