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Back plates like most other M1919 component parts underwent a bewildering number of changes brought about by attempts to produce a better performing weapon or to make use of new materials or manufacturing techniques and to eliminate features no longer required. The buffering systems also went through several design changes eventually adopting a system having virtually no moving parts. In previous articles we have covered the evolution of the M1919 Tank Gun from the M1917 to the M1919 experimental weapons through the M1919A4, M1919A5 and the M1919A6. For those readers that missed that information you can visit the History Page. We will start off this article by visiting the back plate and buffering system of the M1917. The back plate of the M1917 can be removed for field stripping by sliding upward and out of the casing assembly to provide access to the internal parts, and removal of the barrel. It also has a pistol grip to allow the weapon to be trained and elevated when not connected the finely adjustable training and elevation mechanism attached to the tripod. The buffering system is required to absorb the rapid repetitive recoil forces generated by a cartridge that operates in the 50,000 psi range, preventing battering of the bolt against the back plate and either damaging the bolt or the slots in the side plates that hold the back plate in place. With recoil operated weapons it is always a fine design balance between having enough recoil energy to reliably operate the weapon under all conditions likely to encountered, and having the weapon batter itself into junk, which, I would guess to be the worse case reliability problem.  Fig 1 This drawing is detail C of 51-10-17 revision 1 dated Feb. 1, 1919. Note the slot milled horizontally just above the trigger notch the profile of which is shown in Section view B B This cut is for the trigger latch which slid from left to right and had a protruding finger that extended over the trigger preventing it from being raised and firing the weapon. The trigger equipped Browning machine guns with trigger latch installed fire by sliding the trigger latch to the left and raising the trigger upward not pulling it like a conventional trigger. Note that the fine print under steel type shows that one plate is also required by CL 51, DIV 18 which is the M1919 Tank Machine Gun. The Army didn't call the trigger latch a safety because it was not considered one, likely because it did not lock any of the firing parts such as the sear or firing pin. This feature was never popular with the troops and since it was easily removed when the back plate was dismounted it was usually thrown away. When these weapons missing the latch were discovered the latches were replaced only to be discarded again. Finally in May of 1923 the Ordnance Committee (O.C.M. Item 2984) threw in the towel and recommended revising the drawing removing the slot from back plate and removing the latch from the drawings. Goldsmith in Volume 1 pg 200 mentions minutes of an Ordnance Committee meetings in 1929 where it appears the same subject was rehashed, however in this case the Maintenance Division, Field Service was looking for authorization to stop replacing the latches on weapons equipped with the back plate containing the trigger latch slot. Apparently, while the latch had not been required on new made plates since August 1923, they were still being reinstalled on the weapons with original style back plate. The Ordnance Committee concurred with the request and recommended that Field Service proceeded with whatever method they felt practicable to eliminate the trigger latch. Since WWI M1917 production had reached about 70,000 plus spare parts back plates there were a lot of these perfectly good plates in existence and they continued to surface through the end of WWII, and even today are not uncommon.  Fig 2 This is what the back plate looked like after Revision 5 (August 20, 1923) removed the slot for the trigger latch. Sometimes when Ordnance revised a drawing they just crosshatched or lined out things no longer required like Section B B on this detail which showed the cross section of the trigger latch cut no longer necessary.  Fig 3 This drawing 51-10-26 Revision 6 dated January 8, 1921 shows the grip portion of the back plate. After assembling the grip to the back plate and aligning it properly a pin was inserted from the back side of the back plate to hold the grip in the proper position. As you can see the forward end of the buffer tube area is threaded and screws into the back plate. Note that on this drawing and the previous one there are notations about the drawings being superseded by letter prefix drawings. The drawing for the grip became C8457 on June 1, 1931.  Fig 3A Drawing C64002 with an original date of March1933 showing a slightly revised grip design originally intended for the M1919A2 but in 1936 Revision 1 added the M1919A4 Flexible to the drawings pertains to list. This grip is almost identical to the grip shown in Fig 3 except it only has one small hole for the screw that holds the stocks on the grip, no hole for the stock locating pin, a hole in the bottom for the stock spring screw and a "step" in the buffer tube contour. This step was added by Revision 4 with what looks to be a April, 1941 date. The microfilm that this drawing was archived on is badly deteriorated. The original M1917 grip has 2 small holes one for the stock screw and one at the bottom rear of the grip for the locating pin that holds the stocks from twisting on the grip. The production models of the M1919A2 and the M1919A4 used the one piece stock requiring only the hole for the stock retaining screw. In 1922 Ordnance started to implement a new system of identifying drawings and establishing standard sizes of the medium the drawings were prepared on. The idea behind this change over was having only one part to each drawing and selecting the proper size drawing medium for the part being pictured. If the part was used on more than one weapon or item, only one drawing was needed and only one drawing need to be maintained. The letters seen most commonly in small arms drawings range from A size (8 1/2 X 14) to E size which was 40 X the necessary length. For the M1917 it took 19 years to get all of the drawings converted, likely because of Congress and the public's antipathy to a large standing army and budget restrictions caused by the Great Depression. Nearly all of the original letter prefix conversion drawings for the M1917 have a common date of June 1, 1931. Obviously, all of the drawings were not redrawn the same day, this date was likely chosen far in advance, and represented a "drop dead" date rather than the date when the actual drawing was complete.  Fig 3A Photo courtesy of Rollin Lofdahl Remington manufactured M1917 trigger latch back plate assembled with walnut stocks and the top cover latch stop screw.  Fig 3B Matt D Photo On the right is a pre April 1941 C64002 grip having no "step" in the buffer tube with the single hole for stock screw and the hole in the bottom of grip for the stock spring screw. On the left is a M1917 style grip with the stock locating pin.  Fig 4 Drawing 51-10-2 Revision 5 (8-22-34) is the section drawing of a M1917 showing the component parts of the grip, back plate, and buffer system along with many other parts including the original dovetail bottom plate, buffer system and a few other details like the separate T & E bracket attached to the bottom plate. The original buffer system used a combination of 15 fiber discs a cone shaped plug and a tapered brass split ring held in place by the adjusting screw at the back of the buffer tube.  Fig 4A Photo courtesy of Rollin Lofdahl The original brass buffer ring and steel buffer cone, new and still in the grease. The problem of dissimilar metals contacting each other under spring tension would surface later.  Fig 4B The A9374 fiber discs used in the M1919 buffer systems are approximately 1/8 inch thick and just under 1 inch in diameter. Originally this disc design dating from 1917 had no hole in the center. Apparently sometime after December 1, 1926, the date of the original letter prefix drawing for this part, they were fabricated with a 3/16 inch hole in the center. It appears that this hole was required by the vertical buffer arrangement of the of the M1918M1 and M1919 aircraft .30 calibers which generated the letter prefix drawing, however, we do not as yet know the reason for this. The original A9374 drawing also list the M1917 and the M1921 water cooled .50 caliber as using the discs with the holes. There was still another versions of the disc that was 1/4 inch thick and various combinations of thick and thin discs were used in various weapons. Revision 11 to A9374 dated 3-16-38 removed the requirement for the center hole and the disc reverted back to the original design. The material these discs are made from what seems to be like old fashioned hard linoleum and the color varies somewhat as can be seen in the picture.  Fig 5 The left and right hand walnut "stocks" from drawing 51-10-26 Revision 5. Goldsmith in Volume 1 talks about the 1932 testing of several types of stocks made from aluminum and Bakelite. He also mentions a larger and different contour grip shown on a drawing B128438, a drawing not yet located. More information has recently surfaced regarding the two piece aluminum and Bakelite stocks. At the April 23, 1931 ordnance committee meeting held in Washington the committee took up Item 8888 which concerned a suggestion from the Commanding Officer of the Rock Island Arsenal regarding the fabrication of stocks for the M1911 pistol, Browning machine guns and bayonets from aluminum. RIA felt that a considerable amount of money could be saved with the aluminum stocks as they would be more durable than the standard walnut stocks. The committee felt that the aluminum stocks would be worth a trial and Bakelite stocks should also be included in the trials at the same time. However, they felt that a trial of aluminum and Bakelite bayonet stocks would not be necessary, and recommended that not more than 100 pairs each of the M1911 and Browning stocks be fabricated and forwarded to the Infantry and Cavalry Boards for field trial. At the July 1, 1932 Committee meeting it was reported in Item 10010 that the stocks had been fabricated and recommended that 45 pairs of each type be furnished to both the Infantry and Cavalry Boards for a field trial to last not less than 6 months. The balance of the stocks were to be furnished to the Aberdeen Proving Ground for their evaluation. By the August 4, 1932 meeting in Item 10045 the committee decided to also submit 7 additional aluminum and Bakelite stocks of a larger and slightly different contour for field tests alongside the earlier design stocks. These are likely the stocks pictured in B128438 drawing. The final chapter in the aluminum and Bakelite stock story is in Item 11100 considered at the November 16, 1933 committee meeting. Aberdeen reported in favor of the Bakelite stocks as a replacement for walnut grips. The Cavalry Board also favored the adoption of the Bakelite stocks. The Infantry Board likewise favored the Bakelite stock be adopted as a Substitute Standard and also recommended that the aluminum stocks not be adopted. The slightly larger aluminum stocks required by Item 10045 and furnished for trial and identified as "T3 grips" were recommended by both the Infantry and Cavalry to "be not adopted". No mention of the oversize Bakelite stocks being either manufactured or tested was made. The Committee recommended that the Bakelite stocks of standard dimension be adopted as Substitute Standard.  Photo courtesy of "toolman203", 1919a4.com forum. This is the only hard evidence seen so far of the two piece aluminum stocks. There is no provision for the stock spring, so these grips must have been intended for a M1917, M1919 Tank gun, or some other Browning. The escutcheons appear to be press fit German silver as they will not attract a magnet which would be correct for a 1931/1932 production.  Photo courtesy of "toolman203", 1919a4.com forum. Left inside view of the rare aluminum two piece stocks. The grips appear to be cast and have the standard locating pin hole. The semi-circular marks on the back of the grip are the result of the stock being attached to a grip frame with the locating pin removed allowing the stocks to rotate. The aluminum stocks pictured above are very likely one of about 100 pair produced for the 1932/1933 field trials. They survived the testing, disapproval, and a war or two and nearly 80 years before turning up on a parts table at the October 2010 Knob Creek machine gun shoot. There are no drawing numbers or other markings present so it cannot be definitely proven that the stocks are indeed the leftovers from a project started in 1931, however, the preponderance of evidence certainly makes it appear that these are authentic and quite possibly the last surviving examples.  Fig 5A Drawing B17487 Revision 4 (11-20-39) showing the adoption of the "Optional Material" Colt Wood sometimes written as Coltwood. By December of 1942 the optional material instructions were modified to include molding the escutcheons into the stocks.  Fig 6 This illustration is cut of detail A drawing 51-10-26 Revision 7 the "escutcheons" or stock inserts that allow the screw to hold the stocks in place. The same escutcheons were used on the plastic stocks and the one piece aluminum grip used on M1919A4 Flexible model. The requirement for "German Silver", sometimes called nickel silver, which is a nickel copper alloy was dropped in June of 1942 for plain steel with zinc or cadmium plating or a black phosphate finish.  Fig 7 Photo courtesy of Rollin Lofdahl The one piece aluminum stock (grip) C59334 originally developed for the M1919A2. The piece mark on the part is C-59334-2, for reasons not entirely clear sometimes a dash or space was included between the letter prefix of the drawing and the first numeral. Ordnance practice did not provide for anything between the letter prefix and the first numeral however there are many drawings where this practice was not observed. The -2 at the end of the piece mark indicates that this part conforms to revision 2 of the drawing which made minor changes in some dimensions. The SNL's do not usually list the revisions numbers for parts only the drawing number, in this case C59334. This part was developed to convert the M1917 back plate pistol grip for use on the early A2 and A4 and was also used on C64002 grip designed for use with the M1919A2 and M1919A4. The M1917 stock conversion only required removing the stock locating pin from the grip and sliding the new stock on and fastening with the same screw used for the walnut stocks. The finish on this part is black nickel plating although it looks like paint. When the original A2/A4 one piece grip drawing appeared on June 26, 1936 aluminum was not a critical material because we were not at war. However Ordnance was thinking ahead.  Fig 7A C59334 Revision 9 (6-18-42) the last available drawing of the one piece aluminum stock. Revision 7 to this drawing dated 8-27-41 added the note at the bottom referring to a material "Coltrock" a phenolic resin plastic being an alternate material. We think that "Coltrock" was likely "Coltwood" or a similar material developed by Colt's Patent Firearms Co. for the fabrication of revolver grips. Coltwood was specified as an optional material on the drawing shown in Fig 5A the two piece walnut stocks. Coltwood also was used for the grip material on the Colt "Commando" Caliber .38 revolvers furnished to the U.S. government during WWII and continued in use on commercial weapons produced by Colt post war.  Fig 7B It is unknown where the idea for this stock originated, likely it was at Saginaw, this drawing dated April 29, 1942 proposes to make the stock from "malleable iron". Anything with the words malleable iron has Saginaw's fingerprints all over it. Note that it has no number in the drawing number box, and no authorizing signatures at lower right but only a hand written "C59334", indicating that this item probably never reached the production stage. It is unknown if any of these, other than possibly a few samples, were made. If you have one piece grips in your possession check them with a magnet, if they are made of malleable iron they will attract a magnet and will likely be an extremely rare variant. The stock shown in Fig 7 still has the original black paint and you can see the "Spring, stock", as the Army nomenclature system identified it extending out the bottom. There have been several explanations for the existence of this spring steel clip. One theory is that it was used to fasten down the weapon mounted in a ring or other vehicle mount. My personal favorite is that it was included because the M2 tripod's T & E mechanism connection to the weapon was intended to be left attached to the weapon when the weapon was separated from the tripod when being relocated. The T & E was disconnected from the traversing bar on the tripod and swung to the rear and the screw sleeve (stem) was latched into the spring (clip) on the bottom of the stock, the pintle was released and the weapon and tripod separated and moved to a new location. That way the T & E wouldn't be flopping around while you were running trying to avoid being shot. The truth of the matter is that I don't ever recall seeing a combat photo of the T & E being assembled to a M1919A4 but there are probably some out there. The M1917 didn't require this spring clip because the T & E mechanisms on the M1917, M1918 and M1917A1 tripods were not deigned to be removed like the M2 tripod T & E which became the standard tripod for the air cooled Caliber .30's in in 1933. During the transitional developments from the M1919 Tank Gun to the M1919A2 and the M1919A4 several different styles of back plates, stocks (grips) and buffer systems were produced.  Fig 8 This February 1934 picture shows an early M1919A2 style of buffer system. Note the trigger latch back plate, the three small holes in the grip. and a one diameter buffer tube this indicates that the back plate assembly was originally intended for a M1917. The grip shown does not have any checkering and appears to be a slightly different shape than the one shown in Fig 7. Due to the presence of edge wear I do not believe this grip is made of aluminum. Left to right at the top of the picture the buffer parts are adjusting screw, stop, spring, fiber disc (note the hole as the picture was taken in 1934), filler and plate.  Fig 9 The buffer design shown in Fig 8 was brought about by a recommendation from the Ordnance Committee dated 12-27-33. Apparently, during the adoption of the M2 tripod that weighed about 15 lbs there was some concern about the recoil forces on a light mount. The powers that be (or were) remembered that the earlier M1917 and M1918 tripods weighed in around 54 lbs and they must have had concerns that the light M2 tripod would not be conducive to accurate aimed fire. The wording in "6" sounds like the committee was trying to have it both ways which is what committees usually do. The Committee also passed along a request for a redesigned grip.  Fig 10 Time marches on and the development work on the M1919A2's replacement the M1919A4 proceeded. It appears that the desire for some sort of spring buffer system continued. The parts shown in this 1936 photo are back plate assembly with aluminum grip, plunger, plunger spring, spring, stop, fiber disc still with the hole, filler, split ring, tapered cone and adjusting screw. The back plate is the M1917 design with the trigger latch cut. Other than the spring and stop the parts are very similar to the M1917 buffer system design. The stop and spring drawings for the M1919A2 and A4 first appeared on December 23, 1933 and were declared obsolete 3-21-44.  Fig 11 This cut is from SNL A-6 dated May, 1941, paragraph d. (1) , which is a sort of narrative of the development of the M1919A4, explains why the spring/ring/cone buffer system used in the Flexible model was changed by eliminating the ring and cone and substituting a filler like the one shown in Fig 8 at the top second part from the right.  Fig 11A This cut from the 1941 SNL shows the final spring buffer arrangement that eliminated the cone and ring and substituted a "straight filler". These parts were still available in the January, 1944 SNL. However, from 1943 on, the SNL illustrations only showed the 22 disc buffer system that remained with the M1919A4 and A6 until the end of their service life. The spring buffer system shown in Fig 11A caused another change.  Fig 11B Photo of the original M1917 style adjusting screw with two semi-circular detent cuts courtesy of "toolman203", 1919a4.com forum Apparently during testing of this spring buffer system it was discovered that the original M1917 style of adjusting screw having only two plunger detents didn't provide a fine enough adjustment to provide the required 3/32 spacing between the filler and stop.  Fig 11C This is the transmittal letter from the RIA to the Chief of Ordnance requesting the change to drawing B134059 to add two and change the profile of the plunger detent cuts to the adjusting screw. Note the typo transposition of the drawing number in the text of the letter and the correction hand written in the margin. This request resulted in Revision 5 to B134059 the letter prefix conversion drawing of the two cut adjustment screw.  Fig 11D Originally the adjusting screw was required to be piece marked and, as you can see from the "Drawing Pertains To" area of the title block, it was always the standard for the M1917, M1919 Tank Machine Gun, M1919A2, M1 caliber .22 Training Gun and the M1919A4 Flexible. The piece marking requirement was likely eliminated when drawing B169913, the list of parts that were required to be marked, was adopted on April 7, 1941. The M1919A4 Flexible model wasn't the only air cooled game in town. There was also the M1919A4 Fixed model intended to be used in tanks coaxially mounted with the main gun. In a coaxial tank mounting the weapon is trained and elevated with the same mechanism as the main gun. The only difference between the M1919A4 Fixed and Flexible models was the back plate. The fixed model had no use for a grip and removing the grip made the weapon slightly shorter, always a good thing in the close confines of a tank turret. During the development of the Fixed model it was decided not to reinvent the wheel but use the back plate and buffer assembly of the M1919 Browning Aircraft Machine Gun.  Fig 12 A cut from SNL A-6 May,1941 The upper half is the original type of back plate and buffer system from the aircraft gun. The lower is spring buffer style, all of the parts with the exception of the discs and spring/stop are the same. Note the disc in the lower picture with the hole and the discs in the upper picture without. This seems backwards since the lower assembly is supposed to be the later version. The adjusting screw for the Fixed models has a hole in the screw slot just like the aircraft gun and when the A20483 lower buffer is struck by the recoiling bolt the force is transmitted by the 45 degree face cuts on the lower and the A20482 upper buffer from the horizontal to the vertical plane. The adjusting screw for the vertical buffer has a hole in the side for adjusting screw plunger and spring rather than the horizontal buffers which have the plunger and spring hole in the back plate assembly itself.  Fig 12A Photo courtesy of Rollin Lofdahl This is a right side view of the D8261 back plate used on the M1919 Aircraft Gun and the M1919A4 Fixed weapon. The reason that the buffer tube is not aligned parallel with the long axis of the back plate is to allow access to the end of the driving spring rod for disassembly of the weapon. Even canting the top of buffer tube to the left didn't supply enough clearance for disassembly so a groove was milled in the tube to allow the driving spring rod to be depressed with a screwdriver and locked into the bolt. From the looks of this setup I don't believe the driving spring rod could be locked into the bolt using the rim of a cartridge like the M1919A4 Flexible.  Fig 12B The last revision to drawing D8261 was Revision 8 (11-23-41), shown above, and the only weapons shown on this drawing that this back plate was intended to be used on were the ".30 BAMG-M19", the M1919 Aircraft Machine Gun and the M1919A4 Fixed. On May 28, 1942 the Ordnance Department approved an additional air cooled Caliber.30 fixed type machine gun it was assigned the Major Item number 51-114 and the nomenclature of M1919A5. The M1919A5 was designed for coaxial mounting in the M2A4 and M3A1 Stewart light tank which used the M23 mount for the M5 37 mm main gun. This style mount lacked right side clearance for the bolt handle and cover hold open device of the M1919A4 Fixed. Ordnance solved this problem by redesigning the cover hold open device and shifting it to the left side and removing the bolt handle and replacing it with a stud and a bolt retracting bar that operated from the rear of the weapon. Ordnance decided that the A5 didn't need sights or a pistol grip and opted for yet a different style of back plate assembly adopted from the M1918 Browning Aircraft machine gun except for a shorter buffer tube holding only 8 thin (1/8 inch) fiber discs rather than the 7 thick (1/4 inch) and 8 thin discs of the aircraft weapon. This style back plate and buffer system did away the upper and lower buffers, spring and stop parts used in both the early and the late A4 Fixed model and followed the trend to all disc buffers. Only about 4,600 M3A1 tanks were produced before production was halted in October of 1943. However, according to Goldsmith Vol. 1 about 15,000 M1919A5 weapons were produced,. This would explain why so many of the A5's were converted to A4' and A6's.  Fig 13 Not only did Ordnance come up with new style horizontal buffer back plate for the M1919A5 they came up with two versions. B195998 which consisted of three parts the plate, the same one used on the M1919A4, a short buffer tube, and a locking pin. C121040 was a one piece plate and buffer tube combined which did not require a pin to lock the tube to the plate and was fabricated from "WD1045" steel and was not a casting. Both styles have the same original date on the drawings May 28, 1942 and both drawings show that either plate can be used on the M1919A5 and the M1919A4 Fixed models.  Fig 13A1 Rollin Lofdahl photo This photo shows the one piece back plate/buffer tube on the left and the two piece version on the right. The "swell" on the side of the back plate portion of the two piece version is a design feature to reinforce the female threaded section of the back plate. Both types use the B9833 adjusting screw with the hole in the center.  Fig 13A This Saginaw produced experimental drawing dated 4-4-42 proposed to install a compression spring without any stops or fillers along with the 8 discs. The hand written text which is not completely legible refers to a " Spring ? 140 lbs from 0 to ?" Anybody who thinks that they can decipher this please drop me an e-mail at the address shown on the home page. We do not know of any tests involving this design or samples fabricated. Some of the drawings shown in this article, like Fig 13A ,have not been viewed in nearly 70 years and never seen by the general public The next installment of the back plate saga focuses on the one piece buffer tube, grip/stock, top cover latch stop Saginaw casting.  Fig 14 This sketch is a little fuzzy, but is the first mention found so far for the C153469 ArmaSteel cast back plate that eventually replaced all the other variants on the M1919A4 and A6 models. It's dated June 1943 and has "153469" hand written on the face and is titled "Back plate modifications".  Fig 15 Drawing C153469 Revision 6 with an original date of August 18, 1943. It didn't take Ordnance very long to conclude that the one piece cast back plate was a superior design. Casting this part eliminated the grip, stocks, stock screw and latch stop screw and eliminated all the fabricating and assembly work with the older multi-part design. As far as we can tell this back plate assembly never used anything other than the 22 disc style buffer system.  Fig 16 Here's the cast back plate disassembled, only 3 discs are shown in this photo however 22 were used. There is no toothed lock washer shown to lock the stock spring screw in place, and the adjusting screw plunger spring is not shown because I gave up trying to remove it from its recess. The first mention of this cast assembly with an illustration is in ORD 9 SNL A-6 dated April 1947. This 1947 SNL also starts the practice of only issuing the entire back plate assembly including all the parts of the buffer system packaged ready to install listed with an assembly number of C7100059 and a stock number of A006-7100059. Individual parts are shown, but many do not have stock numbers which would prevent them from being ordered. The previous multi-part designs are also listed as "alternates". The toothed lock washer for the stock spring screw is also pictured for the first time in this SNL. This also holds true for both the fixed models, M1919A4 Fixed and M1919A5 Fixed which are shown as sharing the same back plate assemblies with the one piece horizontal tube/plate as the preferred and the two piece horizontal as the alternate. Not only did the cast back plate gain favor as the "preferred" assembly for the M1919A4 and A6 but one was developed for the M1917A1 water cooled that lacked the stock spring and the recess for the T & E sleeve.  Fig 17 Rollin Lofdahl photo. The M1917A1 cast back plate with integral grip is sometimes known as the "short grip" but officially it's drawing C121054. Its intended use is for the M1917A1, however, there are illustrations in the first A6 TM, TM 9-206 September 1943, showing the M1919A6 having this style grip. The truth of the matter is that any of the plates could be mounted on any of the weapons because the casing assemblies were mechanically virtually the same.  Fig 18 This cut is from sheet 5 of the Base Shop Data dismantling instructions for the M1919A4 Flexible. As late as June 1943 all three types of buffer systems were still in the field. There were no instructions to remove and replace the spring or cone and ring style buffers. This illustration shows a M1917 trigger latch back plate and the one piece stock. The earlier requirement for 15 buffer discs with the ring and cone style has turned into 16 discs. There is a directive somewhere, but we haven't found that either.  Fig 19 Sheet 6 from the same BSD shows the buffering system for the M1919A4 fixed model along with both horizontal and vertical buffer tubes. If the M1919A5 or the M1919A6 had a BSD of its own, we haven't encountered it yet. TB ORD 366 Overhaul and Rebuild Standards for Small Arms issued in April of 1949 required that the only back plate assembly to be used on the M1917A1 during the rebuild process was the C121054 cast style. The M1919A4 and A6 had the C7100059 cast back plate assembly listed as the preferred, with the earlier C64010 style using the one piece stock on the grip style back plate as acceptable. The M1919A4 Fixed and the M1919A5 were to use the horizontal buffer back plate with our old friend the vertical buffer tube shown as acceptable. The only authorized buffer system was the all disc style. All of the spring, stop, filler, cone and ring styles were to be removed and replaced. These instructions only covered weapons undergoing rebuilds, many other weapons in storage with old style components were likely issued directly from stores without undergoing a rebuild when the Korean War started in 1950. Additionally, it is likely some of the M1919 air cooled weapon furnished as military assistance item were probably shipped directly from stores without going through an arsenal rebuild. This is one explanation of the wide variety of parts styles, some nearing 100 years of age regardless of some arbitrary point in time, that we encounter when examining these weapons. The last TM for these weapons published in 1969 and the last rebuild manual published in 1970 show only cast back plate assemblies with disc style buffers.  Fig 20 This cut from the April, 1970 Depot Maintenance Work Requirements outlines the proper trigger clearances for the trigger opening in the cast back plate. There are probably TM and FM publications between 1949 and 1969 that show different styles of back plates without regard to what the weapon was supposed to be equipped with. As usual your comments are welcome. 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 Staff. A special thanks to a special person Jodie Creen Wesemann, Museum Specialist-Registrar for her help, encouragement, and sharing the really odd finds. A sincere thank you to the following: Rollin Lofdahl, as always, came through with photos of the actual parts and good advice. Matt D and Russ Brindisi who also provided photos and information. 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 together. 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