American Powders go through three (some say Four) distinct phases.
The first phase goes from the development of Smokeless Powders in the USA in the 1890s, and the very fast , high temperature Powders used in the .30/40 Krag, the 6mm Lee Navy, and then the early .30/06. Some of these Powders were single base, others double base; no flame retardants were used, and the shapes of the individual grains varied.
Just before WW I, Dupont developed the MR ( Military Rifle) type of Tubular Powders, single based, to control better the burning rates, by surface area control ( outside, inside, and length). They also tried different coatings of the Powders, ( Powders with “1/2” added to their Number…WW I MRs had numbers in the 10-18 range.
Then in the 1920s, with improved chemistry, and appreciation of the destructive (to gun barrels) nature of a lot of then current Powders, Dupont, fresh from acquiring a lot of German Information, developed the IMR series of Powders, in the 11xx series, specifically for the new, M1 cartridge ( 173 grain Boattailed, for Long range and MG shooting.)
The IMR series featured Tubular design, flame retardand coatings, and more regular grain size. The Range of Civilian Powders developed was to cater for both the Bulk loading needs of the Ammunition companies, as well as the reloading needs of the growing number of DIY shooters, in the 1920s ans 30s.
BY 1940, such powders as IMR 3031, and 4895 has been developed and fully tested, both Militarily and commercially.The introduction of the M1 garand rifle hastened the development of 4895, as the cartridge for the semi-auto reverted to a 152 grain projectile , similar to the original M1906 cartridge. The requirements of gas operation also mandated a more conrollable burning Powder.
Other, heavier Powders had been made for .50 CAL (#5010 ,)& #4831 for 20mm). Whilst some early batches of .303 British for Britain had been made with #3031 ( it reflected Cordite in its burning efficiency), when the Canadians started loading Boxer primed .303 ( DI headstamp) they used for the most part, a Bulk-supply Powder called IMR 4740 ( never available as a commercial canister Powder, but long used in Australia after the war as a “repacked surplus” powder, for the same range of cartridges as both 3031 and 4895.)
BY the end of WW II, Olin’s patent of “Fluid Manufacture” of Powder ( especially double based) “Ball Powder” gave an alternative to the traditional “Tubular grain” powders then available. Somehow the US had never entertained the use of German style “Flake” Powder ( or “Lamellar Powder” to give it its correct technical name.)
These WW II developments allowed the development of the shorter “T65” .30 cases, and subsequent 7,62 Nato cartridge. The .30 Savage’s case was merely a trial vehicle along the way, in its case size ( 47 mm)…a whole range of case lengths were tried in the US, Britain and Belgium, untill the US eventually settled on 51mm, as the “ideal case”.
Nowadays, IMR Powders have come further, with the development of “Controlled Porosity” of the Nitrocellulose matrix of the grain structure.
This improves Burning rates and flame temperatures. A development of the former Australian Govt Explosives Factory at Mulwala ( set up by Dupont in 1942-3 ( now “ADI-Thales group” , Mulwala). The ADI :AR series of powders are now exported to both Military and sporting ammo factories the world over, and also sold under various “House brands” in the USA, under different names. Hodgdon Powder was a big customer, and ADI even developed a 4895 Clone in AR2206H ( or is it 2208H???) to replace the now extinct Milsurp H4895.
If the 6mm M1895 Lee had been a Post-WW II development, it would have benefitted from excellent , ballistically matched Powders…back in 1895, the early smokeless of the time, was still not suited for small calibre cartridges…
Too fast, too hot, and too unstable in storage.
Rifle Powders have come a long way since the 1890s.