DI = Defence Industries Limited - Ajax, Ontario, Canada.
Founded in Ajax, Ontaria in 1941 and soon became the largest defence industry in North America,

DM = Des Moines Ordnance Plant - Ankeny, Iowa.
Des Moines was owned by the U.S.Rubber Company and operated from 1941-1945. All 'DM' marked shells have the year in two digits like most other manufactures, with the exception of 1944 which is only a '4'. Lots of the die used to stamp the DM started to wear considerable by 1944 and lots of the tails of the last M are missing. With the early 1942 dated shells the markings are all made from the same font dies, on the 1944 examples you will see a variety of minor differences, thickness of letters, damage to dies and even the font size can vary. The last 'DM' 1945 shells to be made where stamped in large thin letters  that are spread evenly with the date numbers around the base. One in each 1/4.

FA = Frankford Arsenal - Philadelphia, Pennsylvania.
Frankford Arsenal is one of the older manufactuers of .50 cals. The plant operated from 1816 until 1977, spanning and impressive 150+ years. The 1939 dated shells have some of the best looking markings, 'CAL 50 FA 39' impressed all around in large thick letters. From 1940 they adopt the standard style that all the other manufactures were doing. I wonder if someone set a presidence and all the others followed suit.  'F A 40', 'F A 41' and F A 43' have no exceptions that I have seen, however with the '42' dated shells you can occasional see a 5 pointed star? Don't worry its not tiny, you won't miss it if you have one. The F   A    42    * being in equal 1/4's. The 1944 dated shells can be both marked as '4' and '44'.

KS = Kelly Springfield, Allegany Ordnance Plant - Cumberland, Maryland.
Kelly Springfield, like Des Moines was a Tire Company, they made ammunition during 1942 and 1943 only (I believe). Both those years have different sized stamps and thickness to the letters and numbers. The layout also varies somewhat.  

LC = Lake City Army Ammunition Plant - Independence, Missouri.
This plant was established by Remington Arms, originally for a testing facility for small arms firing. By the end of 1941 it also went into production to produce .50's as well as other calibres. The 'LC' dies always seem to me like a real hodge-podge of scruffy and inconsistent, patterns, depth of impressions and styles. Also, there a plenty of shells out there with really badly damaged die marks, not only one letter or number but several. I guess nobody really cared about quality control. It is easy to mistake them as different manufactures like 'I C'.  They also used both '4' and '44' during the 1944 production runs. The '45' produced shells have weirdly stamped the date at the top and the L C at the bottom. I guess they just liked to mix things up!

LM = Lowell Ordnance Plant - Lowell, Massachusetts.
Just like Lake City above, this was operated by Remington Arms but for only a short period. The plant only existed between 1942 and 1943. All the cases I have seen to LM markings have been very consistent and uniformed. No variations to report... sorry.

M = Milwaukee Ordnance Plant - Milwaukee, Wisconsin.
Yes another US Rubber Company converted to produce .50's. Again, like so many of these plants it only operated for a few years, 1942-1943. All the shells are marked M and pretty uniformly, the only exception is in the 1943 dates. They are all '43' stamped, however they are usually stamped close together, but there are some variations of the 4 and 3 being placed in equally 1/3's with the D at the top centre 1/3.

RA = Remington Arms - Bridgeport, Connecticut.
As well as setting up small plants for manufacturing all around the US, this plant IS the oldest in the US and still makes these now. Of course with such a prestigious company history comes a nice variation of shells for us to collect and find. I don't know of any from 1939 made for WW2. However the first pattern .50 was produced for the RAF (British) and came in a two dates 1940 and 1941. The full stamping being 'R.A. 1940 .50 CAL Z' and it looks great! These can also be found with a silver coloured anulas. The .50's produced for the Americans to use was stamped in the usual pattern 'RA     41'. 1942 and 1943 had the standard '42' and '43' abbreviations, 1944 came in '4' and '44' types, although you don't typically see many of the '44' types. I'm sure there are 1945 dated shells... but I have never found any... yet!

SL = St. Louis Ordnance Plant - St. Louis, Missouri.
The Western Cartridge Company set up a new plant a few miles away from there original plant to deal with the high demand for these wartime calibres.  It is one of the few companies that we know how many cartridges they produced, an amazing 6.7 billion .30's .50's during the course of WW2! It also has some of the craziest stamping's yet to mention, yet starts of so standard. 1941 starts with the typical 'SL 41' style, just like every other .50 from any other manufacture. Come 1942 you have at least 3 different styles of dies being used and also some wild overstrikes, but not over the top slightly miss aligned. Some that read things like  'SL SL 42 42 SL' or even things like 'SLS 4 2 4 L' making it hard at times to even relate it to St Louis. Weirldly all this nonsense with the overstrikes only seems to be on shells made in 1942! I guess someone may have had a short career or they fixed what ever problem was causing this. The 1943 shells are all standard, 1944 is the '4' type and 1945 comes to a nice thin lightly impressed style. 

SR = Royal Ordnance Factory - Spennymoor, United Kingdom.
The UK's only producer of .50's, the Royal Ordnance Factory at Spennymoor was a pre World War 1 factory that ran until the close of World War 2. I am not sure when they started producing .50's, but believe it to first be in 1942 and this replaced the need for the Remington Company to produce them in that lovely pattern with all the text! These are stamped in a very British style, small neat stamping that either said 'S R 1942 .50' or the .50 being shortened to '.5', the pattern of stamping changed in 1943 to 'SR     43      .50', still as equally as small and neat. The 1944 style mirrors that of 1943 and uses '44', not the '4' as found on American versions.

T = Tikkakoski Arsenal - Finland.
This is by far the rarest of the WW2 .50 cals to find and if anyone has one I would love to include a photograph of the head stamp. These were produced in Finland by Tikkakoski and the need only arose when the USA supplied Finland with Brewster Buffalo fighters to fight the Russians whom they were at war with from 1941, American still being neutral at this point. Neutrally taking sides by supplying one side and not the other ;) I have only seen these online and are marked '12.7 O*  T  42'. The O* is a circle with crossed swords, which I presume is the company logo. I have no idea what dates of these would be available or what variations there could be.

TW = Twin Cities Ordnance Plant - Minneapolis, Minnesota.
Twin Cities produced .50's from 1941-1945 and also other calibres of wartime ammunition for the US military. Most of the TW shells are marked in the typical format, with one exception. The date is at the top and the TW is at the bottom. Why? Who knows!  There are of course variations, larger spaces between the date numbers and TW letters, not quite into 1/4's but close. Deep impressed letters, thick and thin fonts and lots of broken dies in 1942, in particular with the top left of the T, top of the 2 and the last bar of the W, making it almost a backwards N.

U or UT = Utah Ordnance Plant - Salt Lake City, Utah.
Utah Ordnance was the other plant operated by Remington, this  plant was producing ammunition from 1942-43 (so it's reported) and went into standby some point in 1944 and remain like that until 1946, when it was decommissioned and sold off. The markings usually come with just 'U' and the date numbers at 1/3 intervals. However, some of the earliest produced shells have 'UT'. These are not rare, but its nice to know they come from the first batches. I have't seen 'UT' marked shells in 1943 or 1944, but I will check at some point.  There are shells out there produced in 1944. When they shut the plant down in 1944 I don't know, so I have no idea on how many they produced that year. There was also some poorly stamped examples in 1944, very thick, but very lightly impressed. Any from 1944 could be fairly unusual to find. I will have to see if I have any...

WRA = Winchester Repeating Arms - New Haven, Connecticut.

The plant based in New Haven, Connecticut only closed in 2006. This plant made various different styles, types, calibres right up until its closure. Over the years, many efforts were made to improve profitability at the manufacturing facility in New Haven, and the decision to shut this factory was made after exhausting all available options.
The stamping on the WRA .50's seem to come in two types, the first being a more standard style 'WRA   43', the second is a more impressive looking 'CAL .50  W R A 42'. I sadly have no details on when they started producing .50s, only that I have examples from 1942 and 1943.
     Box and 9mm's part of the J.Hewitt collection. (All rounds are inert)
Winchester has an amazing history that started just after the American Civil War. Jumping forwards a little in time and something which has nothing to do with .50's at all, is this interesting little gem. One unusual WWI order for Winchester was from Great Britain for a small quantity of Model 1886 lever-action rifles chambered in 45-90. They were to be used with incendiary ammunition by “aeroplane gunners” to ignite the flammable hydrogen gas filling the German zeppelins that were bombing London nightly. When America was drawn into WWI, the need for rifles to arm millions of Dough-boys headed for Europe was acute. Winchester Repeating Arms quickly modified the Enfield Number 14 Pattern rifle to handle the U.S.-standard 30-06 Springfield cartridge and the U.S. Model 1917 Enfield was born. Some 545,000 of these rifles were produced by Winchester Repeating Arms, making it the most widely used rifle by American troops during the conflict.
Other Winchester Repeating Arms contributions during WWI were the production of 47,000 Model 1918 Browning Automatic Rifles (BARs), modifying the Model 1897 pump shotgun into the famous “Trench Broom” for close-quarters fighting, and collaborating on the development of the .50 caliber cartridge for the M2 Browning heavy machine gun.


Cartridge, Caliber .50, Tracer, M1

Tracer for observing fire, signaling, target designation, and incendiary purposes. This bullet has a red tip.

Cartridge, Caliber .50, Incendiary, M1

This cartridge is used against unarmored, flammable targets. The incendiary bullet has a light blue tip.

Cartridge, Caliber .50, Ball, M2

This cartridge is used against personnel and unarmored targets. This bullet has an unpainted tip.

Cartridge, Caliber .50, Armor-Piercing, M2

This cartridge is used against lightly armored vehicles, protective shelters, and personnel, and can be identified by its black tip.

Cartridge, Caliber .50, Armor-Piercing-Incendiary, M8

This cartridge is used, in place of the armor-piercing round, against armored, flammable targets. The bullet has a silver tip.