CASINGS AND ASSOCIATED PARTS
segment we are going to discuss the M1919 family's assembly that
houses the internal parts of the caliber .30 Browning machine gun.
bottom plate, top plate and trunnion block assembly have been covered in
detail in previous articles in this series.
This offering will
consist of the right and left side plate assemblies, breech cam lock
and cam lock screw.
We will also address the
development of the at least three short round stops their function, belt holding pawl, bracket and pin, feed extractor and extractor
cams and front and rear cartridge stops.
Most U.S. Army Ordnance publications refer to the portion of the weapon that
houses the internal working parts as the "receiver".
It is most often a single piece that connects the barrel and various
other parts of the weapon allowing them to function as a firearm.
Some weapons, like the M16 rifle, consist of a two part receiver the upper,
which is attached to the barrel and houses the bolt and bolt carrier groups
and the lower which houses the fire control and buffer groups and is attached to the
Most times though, when we say "receiver" we
picture something along the lines of the M1903 Springfield, M1 rifle
or M1 carbine receiver.
In our mind's eye we see a chunk of
steel that has been forged and machined to connect the various parts of the
In most cases Ordnance saw things the same way.
Somewhere in Ordnance archives there is a "style book" or some publication
that describes, likely in great detail, how to name things the Army way.
In other words a naming convention that applies the same word or words
to all things Ordnance.
It is not presently known exactly why
Ordnance decided to call the "receiver" of the M1917, the parent of the
subject of these articles a "casing".
The term "casing" may
have been chosen because the "receiver", in this instance, is fabricated from multiple
parts, and Ordnance was seeing the forged chunk of steel and decided that
the image didn't fit the subject at hand and this steel box did encase the
In any event, the combination of parts that make up
the "receiver" of the M1919's is officially referred to as "CASING, assembly,
followed by the model number of the particular weapon i.e. CASING,
Ordnance sometimes used the term "assembly" to
indicate a series of parts attached to each other either by necessity or
The right and left side plates and the trunnion are assemblies.
M1917 and its M1919 derivative's casing assemblies are an assembly of assemblies.
C64222 Revision 9 (12-10-45) the left side plate assembly drawing originally adopted on March 10,
This assembly was used on M1919A4, M1919A5 and M1919A6 weapons.
The M1919A2 used a virtually identical left side plate C64005.
Side plates were not required to be piece marked, however you may encounter
some plates with "L" imprinted inside the left side plate.
These "L" imprinted side plates were produced during WWI
by the New England Westinghouse Company.
The right side plates were marked with "R", however since
the right side plate is the controlled part, and is removed during the
de-militarizing process we seldom encounter them.
At various times during WWII and shortly thereafter some of the
side plate assembly components were available as replacement parts but many
The box on the lower left of the drawings indicated which
parts were not available for field maintenance by marking them with an
You could get either of the extractor cams along with their
attaching rivets, the two short mount adaptor rivets, but not the long rivet
that passed through the trunnion or the mount adaptor itself.
could not order the entire side plate assembly or the side plate either.
seemingly bizarre position on which parts could be replaced and which parts
couldn't had a reason.
That reason was that the field forces
were not equipped to replace the entire side plate assembly and by
association the side plate, belt holding pawl bracket and even the mount
adaptor because it was riveted through the trunnion.
Many of the
rivet holes were reamed at assembly to fit the particular set of parts at
This was done in an assembly jig to hold the parts in the
Ordnance field forces were not equipped with these
However field depot personnel could replace the two mount adaptor
rivets and the rivets that held on the belt holding pawl bracket and the
cams and their attaching rivets if the occasion arose because they were
equipped with various rivet sets and anvils.
After WWII, starting in
about 1947, the Ordnance Department took a different view of things and
further restricted the issue of some parts for field repair because we were
not at war and centralizing ordnance repair into depots was deemed more
Some assemblies like the extractor assembly for the
Browning's were user replaceable units of issue.
If you had an
M1919A4 extractor with a broken ejector you replaced the entire extractor
While ejectors were listed as replaceable parts,
users of the weapon didn't have the ability to change them.
One of the things that complicates any dialogue dealing with
M1919's is that many early M1919A4's were rebuilt from other weapons such as
the 1300 or so 18 inch barreled M1919 Tank Machine Guns, various models of
caliber .30 aircraft guns, M1919A2's and a good percentage of the almost
70,000 M1917 water cooled weapons left over from WWI.
Even at this
late date nearly 80 years after the fact some of these converted weapons are
still surfacing as "parts kits" which are the basis for most all of the
semi-auto replica firearms being produced today.
While the right side
plate, the part that the ATFE considers the receiver and is the controlled
part that is destroyed, the left side plates of many of these converted
weapons live on to ever bedevil their owners.
Extra holes, slots and
special bottom plates used in the conversion process for both the M1919's
and the M1917A1's still exist in sufficient number to raise all kinds of
The two photos above, courtesy of Amish-bob/Ordnance Research Inc., show
the inside and outside of a refinished left side plate that originally
belonged to a M1917 water cooled machine gun equipped with a panoramic sight
base. This weapon underwent the stirrup reinforcement modification and
conversion to a M1919A4 probably serving in WWII maybe Korea and who knows where
else along with a stint with the Israeli Defense Forces.
faint 7.62 and upside down "square U", an IDF property mark that appears at the
top of the plate in the lower picture show IDF conversion to 7.62X51 NATO
Talk about your world traveler!
The second and fourth
holes from the right (front of the weapon) in the top picture or from the
left in the bottom picture were for the reinforcing stirrup retrofitted to almost 26,000 M1917 Brownings post
WWI to correct design deficiencies that appeared during WWI combat use.
These problems are discussed in the Bottom Plates tab in this set of
articles along with the development of the D35392 flanged bottom plate that
uses the other 8 holes on the bottom of the plate, shown in the above
pictures, for attachment rivets.
The slot near the
bottom of the plate accommodated the "dovetail" slip in bottom plate a
feature of the original M1917 carried over into the tank guns and subsequent
derivative designs of the M1919A2 and early prototype A4's, finally being replaced by
the flanged bottom plate mentioned in the paragraph above.
particular sample has the C45965 rear sight base that dates from March 10,
1939, a feature of production M1919A4's
Normally the rear sight
base has the three holes for mounting optical sight base drilled and
tapped in the base before mounting to the left side plate.
In the top
picture it appears that the optical sight mount bolt holes were drilled
after the rear sight base was riveted to the left side plate resulting in
the bolt holes going completely through the side plate.
these "extra" holes or slots were present in left side plates for purpose
built production weapons shown in the first drawing in this article which
only has the rivet holes to mount the rear sight base.
This 1936 photo courtesy of the RIA Museum, Jodie Creen Wesemann, shows a
very early pre-production M1919A4 with a reinforcing stirrup and rear sight base mounted on
the top cover latch along with the 24 inch slotted barrel jacket.
on the subject of "extra" holes in side plates, here's an Israeli Defense
Force modified left side plate. Most of the parts kits available today
are former IDF weapons that the U.S. supplied to Israel as military
This is a Saginaw Steering Gear produced WWII
vintage weapon probably late 1943 to mid 1944.
Note the number of cast parts and the different color
of the Parkerizing at the rear of the side plate caused by heat treatment of
the rear most inch.
The IDF converted these weapons to 7.62X51 NATO
caliber and during the process made a few modifications to the weapon to
improve function with ammunition that it was not originally designed
The extra hole in the left side plate has caused much
speculation in the M1919 community.
Most believe, as I do, that the hole,
because it is almost directly opposite from the bolt latch rivet, was there
to allow the bolt latch rivet on the right side plate to be
The main difficulty with the rivet tightening theory is
that the U.S. Ordnance Department designed a tool for that very purpose that
did not require the drilling of holes in the left side plate.
The tool for tightening the bolt latch rivet on already assembled weapons
can be seen at the Bolt Latch tab in this series of articles.
On new built weapons the bolt latch was likely fastened to the right
side plate before it was assembled to the rest of the casing parts.
the bolt latch and the attaching rivet was eliminated from production
requirements in late May of 1943, by this date about 65%, depending on whose
figures you use, of total M1919A4 production had been achieved.
means that more M1919A4's had the latch than didn't.
rebuilt under Ordnance supervision after August,1949 should have had the
bolt latches removed.
Most of the parts kits advertised include a
bolt latch, which some think is a "safety" which it most definitely is not.
One of several things could explain this situation.
Most of the
weapons the IDF received had bolt latches, which would mean that none of
these weapons went through an Ordnance supervised rebuild which smells a
little fishy, or that the IDF liked the idea of the bolt latch and added
them to weapons where they had been removed or never installed requiring the
hole in the left side plate to peen the rivet.
Since bolt latches
were never required to be, and are
seldom marked with, piece marks or manufacturers identification codes it is
difficult to know who made the latches or installed them.
Another theory is that the IDF drilled out the bolt latch rivet, removed the
latch and using the right side plate rivet hole as a pilot drilled through
the left side plate as part of a fixture to hold the casing while cutting
the belt holding pawl slot to the new dimension for the 7.62 pawl.
replaced the bolt latch and used the left side plate hole to peen a new
Further muddying the waters is the fact that some IDF marked parts kits
don't have the extra hole and some have an additional hole above and to the
rear of the left mount adaptor.
The contrarian school of
thought believes that the hole has something to do with setting head space
because the Israeli 7.62 barrel had a different design barrel locking notches and a
different barrel locking spring that makes setting head space by the USGI
method somewhat difficult unless you have three hands.
7.65X51 NATO cartridge (front) is about 1/2 inch shorter than the U.S. Caliber
.30 cartridge (rear) which required feed way spacers to properly position the
cartridge for extraction from the feed belt.
To prevent feeding problems the IDF designed a slightly wider belt
holding pawl which required that the belt holding pawl bracket, left side
plate and trunnion cuts to be made wider to accommodate the 7.62 pawl.
This photo shows the tool marks from the cut, made with the
casing assembled, that altered the pawl opening.
shown has a USGI Caliber .30 front and rear cartridge stops and a IDF modified bolt,
top cover and belt feed slide and pawl.
This photo, courtesy of Rollin Lofdahl, shows a comparison of the IDF
modified pawl bracket in the upper half of the photo and the USGI
unmodified bracket in the lower along with their matching pawls, springs and
The IDF appears to have used a slightly different pawl
spring which applied more upward pressure to the pawl.
heavier IDF spring sometimes causes feeding issues in semi-auto M1919
conversions requiring either a different spring or removing one or two coils
from the IDF spring.
It is not known why the IDF opted for the
Most IDF pawls can be identified by the marking on
the outside edge which is two Hebrew characters in an oval followed by "7.62".
The IDF modified pawls and other feed system parts, other than the
feedway spacers work equally well with U.S. caliber .30
split pin that holds the belt holding pawl in place, used on all of the air
cooled ground Caliber .30 Brownings and the M18A1 and M19 aircraft guns,
remained virtually the same from the 51-10-29 drawing for the M1917 water
cooled originally dated June 13, 1917 and then became A20566 in 1931 and
finally B147217 on to the end of its service life.
real change was the material from which the pin was made, originally drill
rod which didn't require heat treatment and later W.D. 1095 steel using
various hear treatments and protective finishes.
Odd bits of
information always seem to surface when examining these old drawings.
The original drawing of the pawl pin, 51-10-29, was submitted to the
Ordnance Department by the Link-Belt Co. of Philadelphia, PA
not presently known what the relationship of Link-Belt, who in the WWI era
was a manufacturer of conveyors and agricultural machinery and in later
years as a subsidiary of FMC Corporation manufactured construction cranes
and excavation equipment, was to U.S. Army Ordnance.
In addition to the modifications made by the IDF, there
are differences in the appearances of the belt holding pawl brackets
manufactured by US makers.
The following three photos, courtesy of
Rollin Lofdahl illustrate some observed differences between manufacturers.
This Remington manufactured bracket was likely from a M1917
water cooled Browning.
Another WWI Vet.
This bracket is from a WWII vintage Saginaw M1919.
differences in appearances of brackets from various manufacturers, other
than the second and third IDF modified brackets, they are functionally
The brackets also have rectangular cuts forward and aft of
the belt holding pawl cut.
The front cut, along with the pawl pin is
used to fasten on the "live round stop".
Ordnance developed a blank
firing adaptor that replaced the muzzle plug/front barrel bearing that
allowed the weapon to function using blank ammunition.
blanks provide very little recoil energy this system relied on increased gas
pressure against the front of the barrel, rather than the usual recoil
operated/gas assist operation with service ammunition.
had a very small muzzle opening to create sufficient back pressure to cycle the weapon.
The muzzle opening was so small that it
would not allow a projectile to pass through, and to prevent anything other
than a blank from entering the feed way and creating a potentially lethal
situation, the live round stop was installed first and removed last when
converting the weapon to blank firing operation.
Often the blank firing device
on the muzzle, and the outer end of the live round stop were marked with a
brightly colored paint as a method of visually confirming that these devices
were correctly installed.
In the late 1930's the Army, who at that time
was operating the air force which they called the Army Air Corps, decided
that .30 caliber machine guns lacked the necessary power and range for
either offensive or defensive armament on aircraft and settled on the Browning
.50 caliber as the weapon of choice for Army aircraft.
meant that a sizable number of .30 caliber aircraft type machine guns became
surplus and were thrown into
the pool of weapons to be rebuilt.
A number of these aircraft models
were converted into M1919A4, A5 and possibly A6 weapons.
obsolescence of the Caliber .30 aircraft weapons increased the number of
possible permutations of casing assemblies available for rebuilding into
more desirable weapons.
This photo courtesy of "gearlogo", m1919a4.com forum, shows a left side
plate from a M1918 (Model of 1918) Browning Aircraft Machine Gun that had
the two synchronizer cuts filled with steel plate and the two extra rivet
holes for the reinforcing stirrup, and the "dovetail" bottom plate slot.
The outside of this plate has IDF property marks and was imported
into the U.S. as a "parts kit".
This weapon has had more lives than
the proverbial cat.
Early in WWI when single seat aircraft first
appeared, pilots shot at each other with revolvers, shotguns, and most
anything else that would go bang.
Later, they were armed with
machine guns installed in a fixed forward firing position on the top of the
upper wing so that the line of fire did not strike the propeller.
This type of mounting made it difficult for the pilot to aim, fire and clear
jams or even reload the weapon.
The answer was machine
guns mounted on the cowl of the aircraft directly in front of the pilot.
The drawback to this mounting location was the
considerable problem of shooting off your own propeller.
The French solution to this problem, and I'm not making
this up, was to install metal deflector shields on the propeller blades.
In 1914, Anthony Fokker, a Dutch designer of German aircraft, devised
a better system of preventing you from shooting yourself down.
He developed a method of interrupting the fire of a
machine gun while the propeller blades were obstructing the line of fire.
These devices were called, not
surprisingly, interrupters or "synchronizers".
on a mechanical linkage between the engine crankshaft and the firing
mechanism of the weapon and prevented the weapon from firing when
the propeller blades were in the line of fire.
from drawing 51-16-5 dated November 1, 1918, 10 days before the Armistice
ending combat in WWI, shows the M1918 aircraft left side plate with openings
for the synchronizer.
This cut from a RIA Museum, Jodie Creen Wesemann, provided photo, dated
February 9, 1942, shows an obsolete Caliber .30 Aircraft gun, probably a
into something more useful first a M1919A4 then a M1919A5.
armorers at RIA did a very good job of obliterating the model number on
this New England Westinghouse built aircraft gun.
The belt holding pawl
underwent very few changes in its service life.
B147216 Revision 10, 7-31-44, the belt holding pawl.
"Alternative" method of manufacture on the left. Apparently, the
recess for the pawl spring originally was cut with some sort of special tool
that left a flat bottomed hole.
On December 2, 1942 Saginaw Steering
Gear suggested that using a standard 3/32 drill bit would accomplish the
same thing without making some special tool. Revision 7, 1-6-43 to the
this part drawing adopted that suggestion as the alternative.
Saginaw was forever suggesting ways to decrease cost/increase production like the simple
expedient of using a commonly available drill bit in place of a special made
This is Saginaw's drawing suggesting the use of the drill bit dated 12-2-42
ordnance adopted this suggestion as an alternative method of manufacture 5
Note the conical area at the top of the spring recess
cut caused by the use of the drill bit.
Some times while looking for
something, you find a nugget of information.
one of those nuggets found by Jodie Wesemann while copying drawings that I
Apparently Chrysler's Amplex Division, formed in 1927
to produce "Oilite" sintered copper/tin/graphite bearings requiring no
lubrication, produced some M1919 parts, or at least belt holding pawls.
This drawing suggests that some of the pawls produced by Amplex did not meet
Ordnance Department requirements and the drawing was produced to show the
variance from specification.
Someone at RIA hand wrote B147216 and
filed this drawing with the other "Backfile" drawings of this part.
The final left side plate components are the extractor feed cam and the
Rollin Lofdahl photo
On the left is the extractor feed cam B17469
and on the right is the extractor cam C8452.
The parts are shown in
their correct relationship when installed on the inside of the left side
The purpose of these parts is to guide the extractor
assembly, by means of the spring loaded extractor cam plunger in the
extraction/feeding cycles of the weapon.
The extractor feed cam is
another of those parts that underwent virtually no change in appearance.
However there were changes to material which caused changes to heat
The original part was forged from "C" steel, when this part was converted to
letter prefix drawing in 1931 the material was changed to W.D. 1035 steel
with no required heat treatment.
This cut from drawing 51-10-11 was
another drawing submitted by our friends at Link-Belt.
It is likely that
Link-Belt provided drafting room support to the Ordnance Department during
WWI, but is not known with any certainty.
to B17469 (2-1-38) changed the material to W.D. 1050 and required heat
treatment of the entire part. This revision also changed the piece mark of
the part to B17469-3.
(6-18-42) changed the material yet again and removed the requirement for
heat treating the entire part in favor of case hardening and annealing the
This revision did not result in changing the piece mark
Why this is so in Revision 3 and not Revision 7 is not clear.
This business of changing materials and heat treatments likely were an
attempt to ease manufacturing and increase production while conserving
critical materials, labor and shop/ machine time.
You will note at the upper
rear (left in the drawing) a small semi-circular cut.
The purpose for
this cut is believed to provide a "parking notch" for the extractor cam plunger on the left
side of the extractor assembly.
Pulling the bolt to the rear and
manually aligning the plunger in this cut would catch the bolt and prevent
the it from
closing until the bolt handle was pulled slightly to the rear and released.
I do not believe this to be a particularly good method of bolt hold
back as the slightest bump can dislodge the bolt usually resulting in some
smashed fingers if they happen to be in the wrong place.
Rollin Lofdahl photo
This illustration shows the two styles of extractor
cam commonly seen
51-10-23 at the changeover to letter prefix drawing C8452 June 1, 1931.
The lower style
pictured in the photo is the original design shown in drawing 51-10-23.
The upper extractor in the extractor cam photo dates from
Revision 14 to drawing C8452 (December 18, 1943). This change
which altered the appearance but not the functionality of the part did not
change the suffix number of the piece mark which remained C8452-12.
This change in design was considered "optional" at the
discretion of the manufacturer and the Ordnance District supervising the
production. Since the basic drawing number C8452 never changed, all of
the parts regardless of appearance or piece mark suffix were considered
It is entirely possible that the early style extractor cam
remained in production long after the December 18, 1943 date shown on
The extractor cam also underwent the usual heat treatment
and steel type changes in the place of forging as shown for the original
design part in a continuing effort to speed up production and simplify
manufacture. Apparently the removal of the small lip that was intended
to help guide the extractor was considered unnecessary.
Original drawing C64222 (March 10, 1939).
The title block in the
upper right corner is a little hard to read, but the 'Drg Pertains To" block
lists the M1919A4 Fixed and Flexible and the casing assembly which was
common to both models.
D35411 Revision 14 (5-31-43).
Revision 14 removed the hole for the
bolt latch rivet and changed the piece mark suffix to -14.
drawing is a little dark, however you can make out the Revision 4 and
Revision 10 notations in the upper left hand corner.
Revision 3 (9-3-40) added the heat treating requirement for the rearmost 1 inch of the
right side plate and Revision 10 (6-18-42) dropped the early description for the
method of heat treating and just substituted the phrase "heat treat" added
the requirement to "anneal around two holes" which are the two rearmost
rivet holes one for the rear top plate rivet and one for the rear bottom
Drawing C90722 Revision 2 (1-27-43).
The M1919A5 had its own drawings for
the right side plate side, right side plate assembly and the casing
The only difference in the assemblies are the side plates
the M1919A5 had four extra holes for the retracting handle guides no bolt
latch rivet hole and was marked M1919A5.
This only holds true for
purpose built A5's. Many obsolete aircraft and some rebuilt and new made
M1919A4's were converted to 1919A5's and their side plates were hand stamped
with the new designation.
The M1919A5 was a special purpose
weapon that went out of production in mid 1943 because the its primary use
was on the M3A1 Stewart light tank that was already obsolete when it entered
combat in North Africa in 1943.
There are very few if any unaltered
purpose built A5's in existence most were converted into something more
Conversion to other uses did not
require the filling of the four holes required for mounting the retracting
handle guides so their original configuration sticks out like a sore thumb.
Drawing C94516 Revision 1 (3-11-44) the right side plate
assembly for the M1919A6.
The only observable difference between this right side
plate and the D35411-14 M1919A4 right side plate is the markings.
All of the M1919 right side plate assemblies, along with
the M1917 and M1917A1 used the same
front and rear cartridge stops, mount adaptors (sometimes referred to as
"pintle pads") and attaching rivets.
Design of the cartridge stops attached to the right side
plate remained pretty much
constant except for changes in steel types.
Drawing A24603 Revision 11 (7-22-43). Revision
1 to this drawing changed the steel type from WD 1095 to WD X1335 other than
that the actual appearance of the stop never changed.
This design provided a self rivet feature.
The front cartridge stop hole in the right side plate was
chamfered at 60 degrees on the exterior side and the shank of the stop
was inserted from the inside and peened into the plate and finished flush.
Drawing B131258 Revision 9 (7-31-44).
Revision 9 was an administrative action which merely
cleaned up the previous revisions likely to make the drawing more
The original drawing dated June 1, 1931 was the conversion
drawing from the old Class and Division system to the "new" letter prefix
style and showed the part being made from
WD 1325 steel with no heat treatment. Revision 3 (2-1-38)
changed the steel type to WD 3115 and added the heat treatment requirement.
Revision 6 (6-18-42) replaced the specific heat treating
instructions with the generic "Heat Treat" and the changed the Rockwell
Hardness from 34-46 to 34-40.
Many Ordnance small arms drawings have this same 6-18-42
date that removed the specific heat treating instructions and changed the
steel type likely because the method shown on the drawings became part of the contract
specifications for the part.
Hardening the part could be done in many different ways
and the manufacturers likely complained about being contractually obligated to one method.
The original drawing also did not require piece mark
imprinting which occurred as the result of Drawing B169913, the list of
parts and manufacturer codes required to be marked issued in April of 1940.
This drawing is reproduced in the Markings article on this site.
This cut from drawing 51-10-10 dated June 1, 1931 is the last Class and
Division drawing before conversion to the letter prefix drawing B17462.
The mount adaptor, which remained constant in design, was attached to
both sides of the casing assembly providing wearing surfaces. Note
that the hole in the center called out at a diameter of .5615 was reamed to
9/16 (.5625) after assembly to the trunnion.
After Revision 4
(11-8-40) to the side plate drawing D35410 all of the mount adaptor holes
and the rivet holes for attaching the bottom plates were reamed to final
diameter at assembly to the side plates, trunnion and bottom plate, this procedure
eased assembly and ensured a better fit of the parts.
The USGI bolt
that attached the pintle to the weapon was 9/16.
IDF modified weapons
often have the pintle bolt hole in the casing reamed to 5/8 inch, probably
to relieve worn holes and true the bore alignment with the pintle.
The purists among us often sleeve the
5/8 hole back to original USGI diameter.
One thing to keep in mind is when
assembling a parts kit is to be aware that the mount adaptors furnished with
the kit might not have the same size hole and most semi-auto right side
plates have 9/16 pintle bolt hole.
D35410 Feb 1, 1938 this drawing cut shows the left side
plate for a M1917 with the mount adaptor integral with the side plate.
This method of fabrication would involve machining off the
entire side plate exterior surface leaving just the small area of the mount
adaptor. Why this method of fabrication was actually considered is
Revision 4 (11-8-40) reverted back to the separate
mount adaptor riveted to the side plate. There are not likely very
many of this style of side plate/mount adaptor in existence.
This rather bad photo taken at the RIA Museum is the style
of side plate mount adaptor shown in the drawing D35410 above. Note
the tapered surface of the adaptor.
Drawing 51-10-18 the breech lock cam at conversion to letter prefix drawing
June 1, 1931.
Originally this part was forged from
"C" steel, the replacement drawing B17467 changed the steel type and on
February 1, 1938 this drawing was replaced by C64133.
The change in drawing numbers was
likely driven by a need to show the part in a larger scale which required a
larger medium on which to depict the part.
The rectangular boss on the bottom of
the cam fits into a cut on the bottom plate to locate the cam. This
version has no staking slots for the lock screw. Depot Maintenance
Work Requirements published in 1970 requires all breech lock cams to have
two staking notches.
C64133 also changed the steel type
and added the elaborate description of heat treatment shown in the upper
left. This drawing and all subsequent drawings, requires piece marking
on the bottom surface of the part.
Drawing C64133 Revision 16 (8-7-45).
Revision 15 made a couple of minor dimension/tolerance
changes and Revision 16 added a 30 degree taper to the outside edges of the
bottom surface of the part.
Many Ordnance drawings, like this example, eliminate
heat treating different surfaces of the part in different ways as shown on
the original C64133 drawing.
This was often accomplished by changing the steel type and
treating the entire part.
These changes likely saved a considerable amount of time
and produced more uniform parts.
You will notice that Revision 15 drawing has two notches in the
top surface of the cam at the screw hole. These staking notches were
added by Revision 7 (3-16-42).
This DWO added the staking slots and revised a few other
dimensions on the drawing of the breech cam lock. Sometimes
these documents have a reason for the change spelled out in the text,
however, this one only has the O.O. letters of authorization.
The " O.O.TT" numbers are the Teletype message numbers
followed by the message origination time ( EWT is Eastern War Time a sort of
year around Daylight Savings Time used until September 30, 1945) and the
initials of the person sending the message.
Teletype was the only apparent method of transmitting text
messages in near real time and appears to have been used only in cases of
Because of fear of damage to the breech lock cam or
the bottom plate, it was decided to
back the screw off from hand tight 1/6 to 1/4 turn and staking the screw to
the cam to prevent the screw from loosening to the point of falling out.
TB ORD 366, the small arms rebuild manual (July, 1949),
describes the results of this procedure as: "There will be perceptible float
of the cam".
This was a requirement on all M1919's produced by RIA and Buffalo
Arms, however, it was optional on Saginaw Steering Gear produced weapons.
For reasons not clear at this time, the Saginaw produced weapons
breech lock cam screws were allowed to be drawn up tight and staked.
This cut from drawing 51-10-24 is the drawing superseded
by the letter prefix replacement A20605. The SNL's from 1940, 1943 and
1944 call this the "thin-hd" screw and it was classed as "useable" until the
publishing of the April, 1947 SNL when it was no longer listed as an
Note the concave area at the end of the screw to make the
screw easier to stake to the cam.
Drawing A20527 (April 4 1927) the original drawing of the
cam lock screw. This part was intended for use on the M1919 Aircraft
The SNL's from 1940, 1943 and 1944 refer to this part as
the "thick-hd" screw and the "preferred" part for all of the M1919's.
All of the illustrations in the SNL's show the A20527
Goldsmith in Volume 1 of The Browning Machine Gun presents
some interesting pictures of experimental cast casings for the M1919's.
The cast casing (Figure 429, 430 and 431 pp 398, 399 and 400) was tested in
late 1942 along with a few other cast parts developed by Saginaw.
The cast parts were adopted, however the casing design,
while apparently successful, was not.
Dolf also had a picture of the "RIA Idealized M1919A4"
that he obtained from the Springfield Historical Site dated 1951 that
appears as Figure 516 pp 477.
The SHS photo appears to be a version of the 7 digit
conversion drawing 7144037 Sheet 2 Alternate Construction "A".
Drawing 7145465 Sept 7, 1951 the original 7 digit drawing
of the cast casing now called "Body, Casing".
This drawing was changed by revision "C" (10-28-53) which
added two 10-32 holes and altered the profile of the right side in the area
of the feed way to allow the attachment of a Stop assembly that held the
front cartridge stop on a steel plate rather than rivet the front cartridge
stop directly to the casing body.
You will note that this is an "F" size drawing.
Just to keep things interesting, or for a lack of
something better to do, Ordnance changed the size of drawing mediums again
in about 1952 and the new "F" size 28X40 replaced the old "D" size 24X40
The old "D" size became 22X34 and the rest of the letter sizes also changed.
Apparently, the cast casing never really went away, even
after it wasn't adopted in 1942, and later resurfaced as part of a
program for the M1919's.
This is a cut of the upper left corner of drawing 7145465
showing the proposed markings .
Note that the final model number designation is blank
allowing the use of this part as either a A4 or A6 as the A5 had been out of
production since about April 1943.
This cast body had the trunnion, mount adaptors, bottom
plate and T&E attaching points integral with the casting but used the
original rear cartridge stop and rivet, extractor cams, top plate, rear
sight base, breech cam lock, and screw.
The cast body also provided for a reinforced area at the
rear, formerly heat treated on the right and left side plates, where the
back plate slipped into the mounting grooves.
Drawing 7114037 Sheet 2 showing the "Alternate
Construction "A" the cast body. This drawing is also dated September 7, 1951.
Note the instruction to stamp a "6" in the marking area to
designate the model number.
This version of the cast body or casing required the use of a Stop
assembly A8408715 consisting of a steel plate with the A24603 front cartridge stop
attached and two 10-32 mounting screws (BCLX1.9) which were required to be
staked to the plate.
This change in design likely was required because of the rather
thin area of the casting where the front cartridge stop attaches and the
fact that the front cartridge stop could be replaced by field forces
replacing the plate assembly, which had the stop already attached without
riveting a replacement stop to the cast casing itself and possibly breaking
Sheet 1 of 7114037 is a conventional casing assembly for
There is an identical set of these drawings, which in
early 1951, replaced the old Class and Division drawings used as finding
diagrams for the M1917A1, M1919A4 and the M1919A4E1.
Engineering Change Order 36451, apparently used as a
transmittal letter, to accompany the drawings of the new cast casing
assembly dated 28 September 1951 which provided for the alternate
method of manufacture.
The authorizing authority was a serialized letter from the
Office of the Chief of Ordnance (O.O.472.5/162) dated 5 March1951 ordering the change
(Revision 7) to be effective 9-7-51.
Ordnance maintained the drawings of the cast body until at
least mid 1954, by this time the M1919's end of service life was on the
Since Ordnance had thousands of conventional M1919 casings
it is not likely that other than a few tool room samples of the cast body
were ever produced.
The Army including the Ordnance Department struggled
mightily with the problem of date notation.
In the U.S. we usually use a notation system of
month-day-year i.e. November 2, 2010 or
However, most European nations including Britain
used a system of day-month-year i.e.
2 November 2010 or 2-11-10.
It is easy to see the potential to misinterpret the
notation of 2-11-10 or 11-2-10 is
it February 11th or November 2nd ?
During WWII the U.S.
Armed Forces adopted the method of using day-month-year that everyone else
was using except they always used alpha characters for the month.
It would be difficult to confuse the date written 11 February 2010 with 2
Drawings seemed to have always maintained the
month-day-year method of notation whether or not the month was denoted in
alpha characters or digits.
The ECO presented above shows Ordnance having it both
Another casing part that became a post WWII requirement
was the short round stop.
Drawing B7162248 (March 6, 1946) the original design short
The exact reason for the development of this part remains
something of a mystery.
Where the "short rounds" were coming from?
Ordnance department never changed the physical dimensions for the M2 Ball
projectile or cartridge or as far as we can tell any of the other Caliber .30 ammunition
used in this weapon.
However the short round stop performs as advertised when
attempting to use commercial .30'06 ammunition which tends to be some what
shorter than military ammo.
One reason for this development could have been the
increased use of metallic links by ground forces revealed a need for the
cartridge to be held more securely in alignment in the feed way for the
extractor to pull the cartridge from the links.
This stop was intended to be staked to the existing front
cartridge stop using two 3/32 notches (only the top one is
visible on the top view of the part.)
B7162248 Revision 5 (10-9-52) shows Revision 3
(6-13-51) adding a "finger" to the right rear of the stop. Revision 4
(2-28-52 adding a note about casting the part and revision 5 adding the
casting drawing number .
Originally the M1917 and its derivative designs used only
fabric belts. The M1 metallic links were introduced in 1931, however,
probably as a steel/machine time conservation measure, their use was
restricted to aircraft ammunition until very late in WWII.
The original M1917 used a spring lock type hinge pin that
was secured into a slot cut into back of the trunnion the top cover had no
hold open feature. This spring pin
arrangement was similar to the spring style pivot pin. This evolved into a simple pin with a
knurled head and a cotter pin retainer on the M1919A2 and very early
In 1938 the spring loaded fixed/movable plates with the
shoulder bolt/castle nut/cotter pin cover hold open device was introduced.
Everything was just dandy until the metallic link
ammunition for ground weapons became more prevalent. Apparently
reports about stoppages from links jamming on the fixed plate where it rested on the feed way
came to the attention of the Ordnance establishment.
brought about the usual reaction, testing and the eventual redesign of the
short round stop along with several several MWO's (Modification Work Order) being issued to the field forces
for a fix.
This is a "cut and paste" job done long before computers
existed which replaced the September, 1953 MWO with one dated
September, 1954 which merely added the M1919A4E1 to the list of weapons to
Here's the illustration from the MWO that showed the small
arms repairman what to do.
This wasn't the end of the design changes to the short
The stop on the left is the standard Revision 3 stop.
The one on the right, is the mystery part Stock #
1005-6069673-A006 Drawing number 8413927.
It was manufactured, packed and preserved in 1959 and
instead of the hole to slip over the existing front cartridge stop, it had a
8-32 tapped hole. The screw shown is not the proper mounting screw,
it's just there for illustrative purposes, and no screw was provided in the
package which was sealed. This stop was mounted using a screw likely
staked to the chamfered stop hole in the right side plate.
We have not been able to locate the drawing, as by 1959
responsibilities for .30 caliber machine guns had been transferred from RIA
to the Springfield Armory, and haven't figured if this part was intended as
a maintenance fix to repair loose or missing front stops or served some
As we have seen earlier, after September 1953 all .30
caliber air cooled BMG's, and the M1917A1 were supposed to have a short round
This screw mounted stop is not the one called out for the
plate assembly for the cast body, and it is not mentioned in the 1969 TM or
the 1970 Depot Maintenance Work Requirements document.
This photo, courtesy of the Texas Military Forces Museum,
Lisa Sharik, Registrar, shows A Buffalo Arms M1919A4 SN 279675
converted to M1919A4E1 by RIA with the screw mounted short round stop
installed. You can just see the end of the finger of the short round
stop that extends over the fixed plate to keep links from jamming in the
feed way peeking out.
The head of the short round stop mounting screw appears to
be staked to the right side plate.
Also note the hole for the rivet that held on the
bolt latch which has been removed at some point.
This cut of the casing group parts is from the SNL A-6 (May, 1941).
Note that this is the casing group parts, not just the casing assembly.
This SNL shows the different size orifices muzzle plugs for the front
bearing for the M1 and M2 Ball ammunition and the slotted barrel jacket.
The original casing assembly drawing D35358 dated September 30, 1936
shows the M1919A4 in its original configuration with dovetail bottom plate,
reinforcing stirrup and separate T&E bracket.
redrawn on March 10, 1939 to show the D35392 bottom plate with the riveting
flanges, integral T&E mounting holes and C45965 rear sight base.
March 10, 1939 seems to have considerable significance for the production
model of the M1919A4 as many other parts and assemblies carry this same original drawing date.
The drawing shown above is Revision
8 which added the barrel jacket and screw to the casing assembly drawing
along with the note to solder the jacket to the trunnion.
couldn't seem to make their mind on whether the jacket should be shown on
the casing assembly drawing or not.
Variously dated SNL's show different combinations of parts making up
the casing group.
from ORD 9 SNL A-6, the publication which replaced the previously mentioned
SNL, dated April of 1947 shows a lot fewer parts in the casing group because
some of the parts pictured in the previous photo, like the barrel, jacket,
and bearing and booster plug now had groups of their own.
parts of the casing assembly remained unchanged.
The combination of
parts, top plate, bottom plate, left and right side plate assemblies,
trunnion block assembly, the necessary attaching rivets and depending on
which SNL (Standard Nomenclature List) you are looking at the rear
sight base and its attaching rivets and the breech lock cam and attaching
screw are the component parts of the M1919 casing assembly.
the parts, with the exception of the breech cam lock and screw, barrel
locking screw pawl pin, pawl and spring and top cover latch were available
for field replacement yet the breech lock cam and screw were considered part
of the casing assembly. One more case of slight disconnect between
official definition and actual usage
Ordnance considered the casing assembly to be
"non-expendable" which is a round-about way to say that the casing assembly
IS the weapon.
Nearly everything else is "parts".
Treasury Department's Bureau 0f Alcohol, Tobacco, Firearms and Explosives
(ATFE), however, considers only the right side plate as the "receiver" or
the firearm, likely because that part has the identifying information
including the serial number of both full auto and FFL 07 Dealer/Special
Occupation Tax (SOT) license holder built semi-auto weapons.
CREDITS AND ACKNOWLEDGEMENTS
All of the
Ordnance materials used in the preparation of this article through the
courtesy and cooperation of the Rock Island Arsenal Museum
A special thanks to a special person Jodie
Creen Wesemann, Museum Specialist-Registrar at the RIA Museum for her help, encouragement, and
sharing the really odd
A sincere thank you to the following:
Lofdahl, as always, came through with photos of the actual parts and good
Matt Danker and Tom Chial who also contributed to
The members of the 1919a4.com forum for their encouragement.
Without Dolf Goldsmith and Frank Iannamico's early works on the on the
Browning machine guns this would have been a whole lot harder to put
If you want to know the whole Browning story purchase their