Improved military rifle propellants are tubular

nitrocellulose Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...

propellants A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

evolved from

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

through

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

for loading military and commercial ammunition and sold to civilians for reloading rifle ammunition for hunting and target shooting. These propellants were

DuPont DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...

modifications of

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

artillery Artillery is a class of heavy military ranged weapons that launch munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during si ...

propellants.Davis pp.296&297 DuPont miniaturized the large artillery grains to form military rifle propellants suitable for use in small arms. These were improved during the first world war to be more efficient in rimless military cartridges replacing earlier rimmed rifle cartridges. Four-digit numbers identified experimental propellants, and a few successful varieties warranted extensive production by several manufacturers. Some were used almost exclusively for military contracts, or commercial ammunition production, but a few have been distributed for civilian use in

handloading Handloading, or reloading, is the practice of making firearm cartridges by assembling the individual components (case, primer, propellant, and projectile), rather than purchasing mass-assembled, factory-loaded ammunition. The term ''handlo ...

. Improved military rifle propellants are coated with

dinitrotoluene Dinitrotoluenes could refer to one of the following compounds: * 2,3-Dinitrotoluene * 2,4-Dinitrotoluene 2,4-Dinitrotoluene (DNT) or dinitro is an organic compound with the formula C7H6N2O4. This pale yellow crystalline solid is well known as a ...

(DNT) to slow initial burning and

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...

to minimize static electricity during blending and loading. They contain 0.6%

diphenylamine Diphenylamine is an organic compound with the formula (C6H5)2NH. The compound is a derivative of aniline, consisting of an amine bound to two phenyl groups. The compound is a colorless solid, but commercial samples are often yellow due to oxidiz ...

as a stabilizer and 1%

potassium sulfate Potassium sulfate (US) or potassium sulphate (UK), also called sulphate of potash (SOP), arcanite, or archaically potash of sulfur, is the inorganic compound with formula K2SO4, a white water-soluble solid. It is commonly used in fertilizers, prov ...

to reduce muzzle flash. Davis, William C., Jr. ''Handloading'' (1981) National Rifle Association pp.31–32 1960s nitrocellulose rifle propellant canister

1960s nitrocellulose rifle propellant canister

Reaction mechanism

John Bernadou John Baptiste Bernadou (November 14, 1858 – October 2, 1908) was an officer in the United States Navy during the Spanish–American War. Born in Philadelphia, Bernadou graduated from the United States Naval Academy, Naval Academy in 1880. He wa ...

patented a single-base propellant while working at the

Naval Torpedo Station The Naval Undersea Warfare Center (NUWC) is the United States Navy's full-spectrum research, development, test and evaluation, engineering and fleet support center for submarines, autonomous underwater systems, and offensive and defensive weapons ...

in 1897. Bernadou's

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

with

ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again ...

and

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

was formulated for the reaction pressures generated within

naval artillery Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for shore bombardment and anti-aircraft roles. The term generally refers to tube-launched projectile-firing weapons and exclude ...

. The colloid was extruded in dense cylinders with longitudinal perforations to decompose in accordance with

Piobert's law Piobert's law applies to the reaction of solid propellant grains to generate hot gas. It is stated: "Burning takes place by parallel layers where the surface of the grain regresses, layer by layer, normal to the surface at every point." History ...

. If all external surfaces of the grain are ignited simultaneously, the grain reacts inward from the outside of the cylinder (creating a reaction area of decreasing size), and outward from each perforation (creating a reaction area of increasing size.) Propellant decomposition is initiated by heat causing the colloid to melt and form bubbles of reactive gas which decompose in a luminous

exothermic reaction In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change Δ''H''⚬ is negative." Exothermic reactions usually release heat. The term is often confused with exergonic reaction, which IUPAC defines ...

after the bubbles burst. Rate of reaction is controlled by

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy ( heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conducti ...

through the

temperature gradient A temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location. The temperature gradient is a dimensional quantity expressed in units of degre ...

from the luminous reacting gas through the bubbles to the intact colloid. Heat transfer (and rate of reaction) is faster if the bubbles are under pressure, because heat transfer is more efficient through smaller bubbles. These propellants may not react satisfactorily at low pressures within the

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

-deficient atmosphere of a gun barrel.

Adaptation for use in military rifles

The

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

licensed use of the patent to

for production of artillery propellant for ships operating in the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

, and to

California Powder Works California Powder Works was the first American explosive powder manufacturing company west of the Rocky Mountains. When the outbreak of the Civil War cut off supplies of gunpowder to California's mining and road-building industries, a local manufac ...

for ships operating in the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

. The

United States Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, ...

also used Bernadou's propellant for artillery and for the new

M1903 Springfield The M1903 Springfield, officially the United States Rifle, Caliber .30-06, Model 1903, is an American five-round magazine-fed, bolt-action service repeating rifle, used primarily during the first half of the 20th century. The M1903 was firs ...

service rifle A service rifle (or standard-issue rifle) is a rifle a military issues to regular infantry. In modern militaries, this is typically a versatile and rugged battle rifle, assault rifle, or carbine suitable for use in nearly all environments. M ...

in 1909 with the M1906 bullet. Grain size varied with bore diameter. While artillery grain dimensions might be several inches or centimeters, the standard grains of military rifle propellant were long and in diameter. The Army identified this military rifle propellant as Pyro DG (for diphenylamine, graphited), and 500 tons per day were manufactured by various plants through the first world war.

Package labeling

Military rifle propellant was manufactured in batches in a procedure taking about two weeks from treating cotton linters with

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...

, through curing the extruded grains to evaporate excess ether and alcohol, and finally coating the dried grains with DNT and graphite. Each batch had somewhat different reaction rates, so testing was required to determine the appropriate charge to generate required reaction pressure in the intended cartridge. Test results were forwarded to the factory or arsenal assembling cartridges. Propellants packaged in small sheet metal canisters for sale to civilians were labeled ''Military Rifle Powder'' to distinguish the product from low-density "bulk" propellants intended to react at lower pressures in

shotgun A shotgun (also known as a scattergun, or historically as a fowling piece) is a long-barreled firearm designed to shoot a straight-walled cartridge known as a shotshell, which usually discharges numerous small pellet-like spherical sub- pr ...

s or

pistol A pistol is a handgun, more specifically one with the chamber integral to its gun barrel, though in common usage the two terms are often used interchangeably. The English word was introduced in , when early handguns were produced in Europe, a ...

s and from ''Sporting Rifle Powder'' for early

lever-action The toggle-link action used in the iconic Winchester Model 1873 rifle, one of the most famous lever-action firearms Lever-action is a type of action for repeating firearms that uses a manually operated cocking handle located around the trigger g ...

rifles unable to withstand the pressures of 20th-century service rifle cartridges. Charges of low-density "bulk" propellants were often similar to the volumes of

gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...

used in older firearms and reaction rates were less variable at low pressures appropriate for those cartridges; but each batch of military rifle propellant required a different canister label specifying the batch or lot number with the tested charge weight to generate appropriate reaction pressure in intended cartridges.

Improvements

Orders from countries fighting World War I required determining charges for different European military rifle cartridges, and production volume supported research for improvements. Improved military rifle propellants included a longitudinal perforation converting each grain to a tube with a progressive burning interior surface allowing a more consistent gas generation rate through the reaction period. Early propellants were identified by a two-digit number. As the number of experimental variations increased, each improved military rifle propellant was identified by a four-digit number. In addition to the canisters available from DuPont, the Director of Civilian Marksmanship (DCM) sold surplus improved military rifle propellants to members of the

National Rifle Association The National Rifle Association of America (NRA) is a gun rights advocacy group based in the United States. Founded in 1871 to advance rifle marksmanship, the modern NRA has become a prominent gun rights lobbying organization while cont ...

. By 1936 improved DuPont process control produced batches conforming to published reloading data rather than requiring different charge specifications for each batch;DuPont ''Better Loads for Better Shooting'' (1936) E.I. duPont de Nemours & Company pp.5&6 and those propellants have remained in production. Non-conforming batches were used to load commercial and military cartridges following traditional testing procedures.

World War II

Wartime temporarily interrupted production of civilian specification propellants, as major quantities of new specifications were manufactured. Number 4831 was used to load navy anti-aircraft machine gun ammunition, and number 4895 was used to load United States service rifle ammunition. As these propellants became military surplus after the war, large quantities of different batches were blended together to make products with uniform average performance for sale to civilians. Manufacture of these specifications for civilian use resumed after military surplus had been exhausted; but reaction characteristics were slightly different from the products distributed from military surplus supplies.Hagel, Bob ''Propellant Profiles'' (1982) Wolfe Publishing Company p.113

Specification numbers

IMR® is a registered trademark of the IMR Powder Company assigned to the

Hodgdon Powder Company The Hodgdon Powder Company began in 1952 as B.E. Hodgdon, Inc., and has become a major distributor of smokeless powder for the ammunition industry, as well as for individuals who load their own ammunition by hand. The company's corporate office a ...

, which markets powders under that name.

Sources

* * *

Notes

External links

IMR powders
{{DEFAULTSORT:Improved Military Rifle (Imr) Explosives Firearm propellants