Pistol Brass-Alloy used and Annealing Processes

I just had a question on the alloy used in modern (1990 and later) 9x19mm brass cases (both US and foreign), and the annealing processes, and I have no idea.

Has anyone out there any information on the alloy used by the various manufacturers of cases and the annealing processes. I suspect there are a number of brass suppliers but I don’t even know if Olin and Starline for example have their own Specifications for the brass they buy or is there some standard commercial specification that they both buy their brass against. Any thoughts would be helpful.

I know that there is a DOD Mil Spec MIL-C-50D for case alloy which may or maynot be used by Olin and Starline but I have no idea how that compares with what Agulia, CBC and RUAG use.



Dear Lew, the old standby, 70/30 Cu-Zn, still applies to nearly all brass for cartridge manufacture over all calibres…some heavy duty (Cannon type) brass will go to 72/28 ( different "springiness) and the older (German) 67/33 is still in use for a lot of Rifle cartridge brass.

If one looks at Milspec (USA) brass, the Major commercial makers, which do both Commercial and Military orders, will most probably stick to the one specification ( ie, by default, Milspec). This ensures consistency and economy of brass mill production, and interchangeability of “Military” Brass into Civilian sales ( ie, “job over-runs”).

As to the Pistol brass, due to the lesser number of “draws” required, there is also less annealing required.
Normal annealing is done at “Punch & Cup” stage, and then (if necessary) before Heading/Bunting/Primer Pocket final Form stage.

No final anneal is required on cylindrical cases (most Pistol calibres,) and those rare Bottle-necked Pistol calibres don’t need any anneal either after necking…not like Rifle cases.

Remember, Military (pistol) cases are meant to be “once use”…I think the same procedure would apply to Starline whose primary purpose is the supply of “Reloadable” cases, and in Pistol straight cases, a Neck anneal is not required ( case necks are still soft from the Pre-Bunt anneal.)

Annealing of Pistol cases ( whole Body) is necessarily carried out the rotating mesh cylinders in a furnace, followed by dumping in cold water and an acid pickle to remove scale, before further forming etc.

Differential annealing ( Rifle cases) necessitates specific machinery, to keep the Workhardened head unaffected by Neck and shoulder annealing.

I think full specs may be available from the major makers if one requires a quote for several million rounds…But otherwise, I would say, on the basis of Industrial and Commercial economics, the MilSpec requirements are pretty close to the mark at least where US production is concerned ( or any other Country supplying to US Milspec standard.).
The European (CIP) standards ( and NATO-Spec) would be similar if not identical.

Doc AV
AV Ballistics.

George Frost’s book “Ammunition Making” provides an excellent overview of the complete case-making process and discusses brass characteristics and treatment. I’d suggest anyone reading this should have a copy of Frost’s book, as its title is exactly what is covered in detail. See openlibrary.org/books/OL11504385 … ion_making for possible sources. It was originally published by the NRA, but I don’t see it on their website.

Olin has their brass plant in East Alton (near, but separate from, the ammunition plant), and I understand they supply cartridge brass to other ammunition manufacturers (than Winchester). There may well be other manufacturers of cartridge brass, but I have no knowledge about that. Olin’s is the only one I’ve seen.

I would be interested in knowing if there is anything different about Starline generic pistol brass as compared to other brand brass (including the contract stuff that Starline makes with other headstamps and if it is different at all from their generic stuff). I ask because I have noticed spotting and discoloration quality issues several times with generic Starline brass much more than any other brass.

Frost, in his book, mentions that Olin ( Western) did set up their own Brass mill,( in the 1930s) to make their own coils to their own specs, and also improved their “break down” mill to convert Slab brass into coil sheet. ( Hot two-way rolling)

A Lot of Case-Makers these days buy their Cups already Blanked and Cupped by a general brass Mill, rather than have the expense of Heavy duty double-action (Bliss) presses to Punch and form the cups from sheet coil brass.
PoongSan of Korea is a known supplier of Cups to Milspec sizes (7,62 Nato, 5,56 Nato, 9mm Para,.50 cal etc.); so is the South African Factory ( ?Denel?). IMI ( ammunition) is also known to supply raw cups when requested. I know that Bertram Bullets ( the Specialist Case makers) buy in their cups from various suppliers outside Australia.

Mottling etc of the finish may be a function of the final cleaning of the brass ( acid or other solvent) rather than metal composition. Even Water on brass can cause a Mottling effect…some of the more caustic soap solutions used in both Washing and Lubricating can also affect finish.

We use large quantities of Starline Pistol cases for making Movie, Theatre and Athletic Starter Blanks… some of which can be trimmed and re-used several times (each time producing a shorter Blank–a process only suitable for Rimmed Revolver cases.).
We find that the “reloadability” of Starline brass to be excellent, surpassing all the other US Commercial brass ( and equal to that of CBC Magtech)…not that we favour one against the other…we use what we can get in quantity ( 50K at a time or more).

Doc AV
AV Ballistics.