Improved Military Rifle (IMR)
Encyclopedia
Improved Military Rifle describes a series of tubular nitrocellulose
Nitrocellulose
Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton...

 smokeless powder
Smokeless powder
Smokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...

s evolved from World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 through World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 for loading military and commercial ammunition and sold to private citizens for reloading rifle ammunition for hunting and target shooting. IMR powders are coated with dinitrotoluene
Dinitrotoluene
2,4-Dinitrotoluene or Dinitro is an organic compound with the formula C6H32. This pale yellow crystalline solid is well known as a precursor to trinitrotoluene but is mainly used in the polymer industry....

 (DNT) to slow initial burning and graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

 to minimize static electricity during blending and loading. They contain 0.6% diphenylamine
Diphenylamine
Diphenylamine is the organic compound with the formula 2NH. It is a colourless solid, but samples are often yellow due to oxidized impurities.-Preparation and reactivity:...

 as a stabilizer and 1% potassium sulfate
Potassium sulfate
Potassium sulfate is a non-flammable white crystalline salt which is soluble in water...

 to reduce muzzle flash.

IMR # 3031

IMR # 16 appeared in 1916 with grains 0.03-inch diameter and 0.085 inches long. Through World War I this powder, and the similar IMR # 17, were used to load military rifle cartridges for France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, and the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

. In 1923 IMR # 17½ added 2% tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

 to IMR # 16 to reduce metal fouling from cupronickel
Cupronickel
Cupronickel or copper-nickel or "cupernickel" is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. Cupronickel is highly resistant to corrosion in seawater, because its electrode potential is adjusted to be neutral with regard to seawater...

-jacketed bullets. Grains of 0.03-inch diameter were 0.084 inches long with 8% DNT coating. IMR # 3031 replaced IMR # 17½ in 1934. IMR # 3031 is intended for mid-range loads and medium sporting and military cartridges like the .257 Roberts
.257 Roberts
The .257 Roberts a medium powered .25 caliber cartridge known affectionately as the Bob. It has been described as the best compromise between the low recoil and flat trajectory of smaller calibers such as the .22 and 6mm, and the strong energy but not the strong recoil of larger popular hunting...

, .30-30 and .348 Winchester
.348 Winchester
The .348 Winchester is an American rifle cartridge. It was introduced in 1936, and developed for the Winchester Model 71 lever rifle. The .348 was one of the most powerful rimmed rounds ever used in a lever rifle.-Performance:...

. Grains of 0.029-inch diameter are 0.083 inches long with 7% DNT coating.

IMR # 4064

The first IMR powder, IMR # 15, was designed in 1914 as a replacement for cordite
Cordite
Cordite is a family of smokeless propellants developed and produced in the United Kingdom from 1889 to replace gunpowder as a military propellant. Like gunpowder, cordite is classified as a low explosive because of its slow burning rates and consequently low brisance...

 for the .276 Enfield
.276 Enfield
The .276 Enfield was an experimental military rifle cartridge developed in conjunction with the Pattern 1913 Enfield rifle. Development was discontinued by the onset of World War I.-History:...

 cartridge. Grains of 0.032-inch diameter were 0.084 inches long with 9% DNT coating. In 1919 IMR # 15½ added 2% tin to IMR # 15 to reduce metal fouling from cupronickel-jacketed bullets. IMR # 4064 replaced both powders in 1935. IMR # 4064 is intended for magnum capacity cartridges like the .250-3000 Savage
.250-3000 Savage
The .250-3000 Savage is a rifle cartridge created by Charles Newton in 1915 and is also known as the .250 Savage. The name comes from its original manufacturer, Savage Arms and the fact that the original load achieved a 3000 ft/s velocity with an 87 grain bullet.-Background:Charles Newton...

, .35 Whelen
.35 Whelen
The .35 Whelen is a powerful medium-bore rifle cartridge that does not require a magnum action or a magnum bolt-face. The parent of this cartridge is the .30-06 Springfield, which is necked-up to accept a bullet diameter of...

 and .375 H&H Magnum
.375 H&H Magnum
The .375 Holland & Holland Magnum is a powerful rifle round and one of the best-known and most popular medium-bore cartridges in the world. The .375 H&H was only the second cartridge ever to feature a belt, now common among magnum rounds. A popular misconception is that the belt is for headspace,...

. Grains of 0.031-inch diameter are 0.083 inches long with 6.5% DNT coating.

IMR # 4198

Military Rifle (MR) powder MR # 21 appeared in 1913 for loading traditional sporting cartridges including the self-loading .25
.25 Remington
The .25 Remington is an American rifle cartridge. A rimless, smokeless powder design, this cartridge was considered to be very accurate by period firearm experts and suitable for game up to deer and black bear....

, .30
.30 Remington
The .30 Remington cartridge was created in 1906 by Remington Arms. It was Remington's rimless answer to the popular .30-30 Winchester cartridge. Factory ammunition was produced up until the late 1980s, but now it is a prospect for handloaders...

 and .32 Remington
.32 Remington
The .32 Remington is an American rifle cartridge. A rimless, smokeless powder design, this cartridge was once considered to be suitable for game larger than deer and black bear...

 and the .22 Savage Hi-Power, .25-35
.25-35 Winchester
The .25-35 Winchester, or WCF was introduced in 1895 by Winchester for the Winchester Model 1894 lever action rifle...

 and .30-30 for lever action rifles. Grains of 0.03-inch diameter were 0.04 inches long. Over the next decade MR # 21 was replaced by IMR # 18 with 0.03-inch diameter grains 0.05 inches long. IMR # 4198 appeared in 1935 as a replacement for IMR # 25½. Comparatively little information has been released concerning IMR # 25½, since DuPont
DuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...

 never sold it to handloaders. IMR # 4198 is intended for short range loads and medium capacity cartridges like the .300 Savage
.300 Savage
The .300 Savage cartridge is a rimless, .30 caliber rifle cartridge developed by the Savage Arms Company in 1920. It was designed to replace the less powerful .303 Savage in their popular Savage Model 99 lever-action rifle...

, .32 Remington, and .32 Winchester Special
.32 Winchester Special
The .32 Winchester Special is a rimmed cartridge created in October 1901 for use in the Winchester Model 94 lever-action rifle. It is similar in name but unrelated to the .32-20 Winchester cartridge ....

. Grains of 0.026-inch diameter are 0.083 inches long with 4.5% DNT coating.

IMR # 4227

IMR # 1204 powder appeared in 1925 for short lever action cartridges like the .25-20
.25-20 Winchester
-External links:* * *...

, .32-20, .38-40, and .44-40. Grains of 0.025-inch diameter were 0.021 inches long with 8% DNT coating. IMR # 4227 replaced IMR # 1204 in 1935 for small capacity cartridges like the .22 Hornet
.22 Hornet
The .22 Hornet is a low-end vermin, small-game and predator centerfire rifle cartridge. It is considerably more powerful than the .22 WMR and the .17 HMR, achieving higher velocity with a bullet twice the weight. The Hornet also differs very significantly from these in that it is not a rimfire...

, .25-20 and .32-20. Grains of 0.024-inch diameter are 0.023 inches long with 6.5% DNT coating.

IMR # 4320

IMR # 1147 appeared in 1923 for military cartridges like the .30-06 Springfield
.30-06 Springfield
The .30-06 Springfield cartridge or 7.62×63mm in metric notation, was introduced to the United States Army in 1906 and standardized, and was in use until the 1960s and early 1970s. It replaced the .30-03, 6 mm Lee Navy, and .30 US Army...

 and the 7.92x57mm Mauser
7.92x57mm Mauser
The 8×57mm IS is a rimless bottlenecked rifle cartridge. The 8×57mm IS was adopted by the German Empire in 1905, and was the German service cartridge in both World Wars...

. Grains of 0.034-inch diameter were 0.042 inches long with 8% DNT coating. IMR # 4320 replaced IMR # 1147 in 1935. Grains of 0.034-inch diameter are 0.042 inches long with 6.5% DNT coating. IMR # 4320 is intended for large capacity sporting and military cartridges like the .220 Swift
.220 Swift
The .220 Swift is a semi-rimmed rifle cartridge developed by Winchester and introduced in 1935. It was the first factory loaded rifle cartridge with a muzzle velocity of over...

, .270 Winchester
.270 Winchester
The .270 Winchester was developed by Winchester Repeating Arms Company in 1923 and unveiled in 1925 as a chambering for their bolt-action Model 54. The cartridge is based upon the .30-06 Springfield...

 and .30-06

IMR # 4350

In 1910 MR # 10 was designed for the .280 Ross
.280 Ross
The .280 Ross, also known as the .280 Nitro, .280 Rimless Nitro Express Ross and .280 Rimless cartridge, is an approximately 7mm bullet diameter rifle round developed in Canada by F.W...

. Large grains 0.033-inch diameter and 0.12 inches long were intended to slow the burning rate. MR # 10 was replaced by IMR # 13 in 1917 for high-capacity bottleneck cases. Grains of 0.035-inch diameter were 0.08 inches long. IMR # 4350 replaced IMR # 13 in 1940. Grains of 0.038-inch diameter are 0.083 inches long with 5.5% DNT coating.

IMR # 4831

IMR # 4831 was used to load Oerlikon 20 mm cannon
Oerlikon 20 mm cannon
The Oerlikon 20 mm cannon is a series of autocannons, based on an original design by Reinhold Becker of Germany, very early in World War I, and widely produced by Oerlikon Contraves and others...

 cartridges through World War II. Salvaged powder became available to civilians when the Oerlikon cannon was declared obsolete following the war. Grains of 0.038-inch diameter are 0.083 inches long with 7% DNT coating. IMR # 4831 contains 1.1% diphenylamine (0.5% more than other IMR powders.)

IMR # 4895

Originally known as 1909 Military or Pyro DG (for Diphenylamine Graphited), 500 tons per day of MR # 20 was manufactured for military loading of the original 150-grain M1906 bullet in the .30-06 through World War I. Grains of 0.03-inch diameter were 0.084 inches long with 9% DNT coating. IMR # 1185 was used when military .30-06 loadings shifted to the 173-grain M1 bullet from 1926 to 1938. Grains of 0.032-inch diameter were 0.084 inches long with 7% DNT coating. IMR #4895 was used for loading the 152-grain M2 bullets in the .30-06 through World War II. Grains of 0.032-inch diameter are 0.056 inches long with 5.5% DNT coating.

Trail Boss

IMR Trail Boss is a bulky powder created in 2005 for use in older cartridges. Old cartridges designed for blackpowder have a lot of empty space when using modern smokeless powder. IMR created Trail Boss to be bulky enough that handloaders are not able to accidentally double-charge a cartridge. The unique donut-shaped grains are part of what make the powder so bulky.
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