Editing M1 helmet (section)

=== Shell ===
[[file:M60 101st Airborne Division Exercise 1972.jpg|thumb|left|[[101st Airborne Division]] soldiers wearing M1 helmets during a [[training exercise]] in 1972]]

The non-magnetic [[Mangalloy|Hadfield manganese steel]] for M1 helmet shells was smelted at the [[Carnegie Steel Company]] or the Sharon Steel Company of [[Pennsylvania]]. After being poured into fifteen-ton ingots (also called "heats"), the steel was divided into 216-inch by 36-inch by 4-inch blocks, known as "lifts," which were then cut into three equal 72-inch pieces to make them easier to handle. The cut lifts were sent to the [[U.S. Steel|Gary Works]] in [[Gary, Indiana]] for further processing, after which they were each reduced into 250 68-inch by 36-inch by 0.044-inch sheets, which were cut into 16.5-inch circles. The helmet discs were oiled and banded into lots of 400 for delivery by rail to McCord or Schlueter for pressing and final assembly.<ref>{{cite journal|last1=Giles|first1=Marc|date=2018|title=M1 Helmet Lot Numbers|journal=Military Collector and Historian|volume=70|issue=3|pages=258}}</ref>

Each "heat" of steel was assigned a unique number by the smelter, as was each of its "lifts". When each new heat was unloaded at McCord or Schlueter, it was assigned a sequential number, and each lift within the heat was assigned a letter of the alphabet (for example, the third lift unloaded of the forty-ninth heat received by McCord would be 49C). This unique "lot and lift" number was stamped onto each helmet produced from the discs of a particular lift, and allowed for traceability in case the helmets exhibited defects. The "lot and lift" number is in reference to the time when the fabricator received the helmet discs, not when they were made into finished helmets. Lifts of heats were not loaded onto or unloaded from railcars in any particular order, and were often warehoused (also in no particular order) before being finished.<ref>{{cite journal|last1=Giles|first1=Marc|date=2018|title=M1 Helmet Lot Numbers|journal=Military Collector and Historian|volume=70|issue=3|pages=260}}</ref>

The helmet discs were [[Drawing (manufacturing)|drawn]] to a depth of seven inches to create the rough helmet shape, or "shell," and the edges were trimmed. The edge of the shell has a crimped metal rim running around it, which provides a smooth edge. This is usually known as the "rim". The rim has a seam where the ends of the strip meet. On the earliest shells the seam met at the front. This was moved to the back of the rim in November 1944<ref>{{Cite web|url=http://www.hardscrabblefarm.com/ww2/dating_m1.htm|title=Dating the M1 Steel Helmet|website=www.hardscrabblefarm.com|access-date=2019-05-05}}</ref> At this time, the rim also went from being made of stainless steel to manganese steel. On each side of the shell, there are stainless steel loops for the chinstrap. Early-war production shells had fixed rectangular loops, and mid-war to 1960s helmets feature movable rectangular loops; this feature was adopted in 1943 to address the problem that when earlier helmets were dropped, the fixed loops were more susceptible to breaking off. Early shells for paratrooper helmets feature fixed, D-shaped loops. The shells were then painted with flat Olive Drab shade 319 (1941–1966) or Munsell Y10 green paint (1966 onward), with the paint on the outside of the shell sprinkled with either finely ground cork (World War II era) or silica sand (postwar).

[[file:Albert Hoeben RMWO.jpg|thumb|upright|An M1 helmet with camouflage cover worn by a [[Netherlands Marine Corps]] corporal in 1945]]
World War II-production helmets feature sewn-on cotton web olive drab shade 3 chinstraps, replaced gradually throughout 1943 and 1944 with olive drab shade 7 chinstraps. 1950s and later production chinstraps are made of olive drab webbing attached to the loops with removable metal clips. Nylon chinstraps were introduced in the U.S. military in 1975. These straps featured a two-piece web chin cup and were fastened by a metal snap rather than buckle.<ref name="Brayley2008_p.123"/>

Many soldiers wore the [[webbing]] chinstraps unfastened or looped around the back of the helmet and clipped together. This practice arose for two reasons: First, because hand-to-hand combat was anticipated, and an enemy could be expected to attack from behind, reach over the helmet, grab its visor, and pull. If the chinstrap were worn, the head would be snapped back, causing the victim to lose balance, and leave the throat and stomach exposed to a knife thrust. Secondly, many men incorrectly believed that a nearby exploding bomb or artillery shell could cause the chinstrap to break their neck when the helmet was caught in its concussive force, although a replacement buckle, the T1 pressure-release buckle, was manufactured that allowed the chinstrap to release automatically should this occur. In place of the chinstrap, the nape strap inside the liner was counted on to provide sufficient contact to keep the helmet from easily falling off the wearer's head.<ref>{{cite news |last=Tagliavini |first=Michele |url=https://www.theguardian.com/notesandqueries/query/0,,-2696,00.html |work=[[The Guardian]] |location=London |access-date=8 March 2013|title=STAGE AND SCREEN In all those Hollywood war films, and in quite a few newsreels, the GIs wear helmets but never fasten the straps. Is this bravado, bad discipline or artistic licence?}}</ref>

The design of the bowl-like shell led to some novel uses: When separated from the liner, the shell could be used as an [[entrenching tool]], [[hammer]], [[washbasin]], [[bucket]], [[bowl]], or [[seat]]. The shell was also used as a [[cooking pot]], but the practice was discouraged as it would make the metal alloy brittle.<ref>{{cite web|last=Pike|first=John|title=M1 Steel Combat Helmet and Liner|url=http://www.globalsecurity.org/military/systems/ground/m1-steel-pot.htm|work=GlobalSecurity.org|access-date=8 March 2013}}</ref>