Any such thing?

Machined brass cases are generally too soft for high-pressure cartridges, and factory brass is made by stamping. This work-hardens the brass. The case head is left un-annealed in the final product so that it remains hard.

Can the same hardness be achieved by heat treatment of machined cases? In metal shop, we annealed brass by heating and quenching. I know steel can go either way (anneal or harden), but does brass only anneal when heated?

I guess it would be extremely uneconomical for a manufacturer to make commercial cartridge cases on a lathe, but it is also very uneconomical for an ordinary shooter to tool up to stamp out cases.

H. C.

Steel hardens by a different mechanism. Why not start with harder brass for your cases?

Sorry but any brass that is harder or stronger cannot be formed into a case shape. All you can do to get tougher cases for high preasure loads is shoot them 3 or 4 times with moderate loads then anneal the necks and your Warbird or whatever will love you.

Austin

First let me correct a myth -brass is annealed at temperatures starting about 450 F, it makes NO difference whether you quench or slow cool.This is a myth thats at least 50 years old but you can experiment and learn in a few minutes. Cartridge brass (70CU ,30ZN) is formed into cases by what is called back extrusion.Brass hardens by working, you cannot harden it by heat treating. To machine cases you have to start out with work hardened brass then anneal the neck.

From my understanding mete is right. There are some brass(s) that can be heat hardened BUT 1)I dont believe any are strait zinc/copper alloys but rather AlCu, AlMgCu etc. 2) The process is "Age hardening" a lower temp. one beyond most peoples control as it is fairly prescribed. 3) It is a totally different process than Fe alloys in that it is a BASED on reorganization of the precipitates/crytalline matrix of the alloy. 4) It is not as *strong* as work hardened, or planished brass but is less likely to have a internal failure of sorts... slips etc.
Hope I got that right mete, though I am not that far.

mete,

Thanks for straightening that out. That bit about work hardening it first, then machining, then annealing the necks it makes a lot of sense.

H. C.

Henry--the machined cases are good for 25-35,000
psi depending on how thick they are built..Annealing the top of case will toughen it
because you can work it by shooting and resizing.
But you can't get base work hardened to the levels
of drawn brass, say like 50,000 psi.If base is annealed it goes soft, even on drawn cases, and loses strength.But machined cases are great for BP
and old express cartridges.Ed.

Henry, you would BUY brass, already work hardened ,in 1/2hard, 3/4hard condition. Smallfry, some copper alloys can be heat treated because they are precipitation hardening types such as beryllium copper which is capable of very high strength. Cartridge brass is picked for making cases because it is the most ductile of the brasses.

My machined 1/2 hard Brass cases are acting like they are getting harder and harder after 3 reloadings. I'm still keeping pressures in them to below 38 Kpsi.-Rob

Rob--It would be interesting to see what pressure
they would take after 4 more firings.Maybe there is such a thing in big based cases, having the
space in the cross section,the grain structure
maybe could orient better for toughness. To work harden or toughen to be usable at
a lot higher pressures.And usable at higher pressures as long as the primer pocket stayed the same, during the multiple firings used to toughen
the case.Maybe you can find out.Ed.

The case made by back extrusion have been worked to a great extent and the grain structure becomes directional which benefits the strength. The hardness ,grain size and grain direction are carefully controled in making the case. This is something that cannot be done with machined cases. As for hardeing during firing ?When firing the ,the case will harden only if it stretches.

Mete--That has been my understanding also, the brass has to stretch. That is why I was curious
about big cases, when fired, if maybe the base would flatten a little out as well as in to keep primer tight.This flattening thus perhaps working the brass enough to harden it.

When I developed my wildcat 458 I had soft Bell extruded brass that seemed to get harder and take 50,000 psi loads after fired 7 times with 35,000 psi loads.If fired in my testing with a
50k load the first time the primers would be loose and belt expanded .002.

The sides of the case get worked in firing and resizing to become tough, even machined cases, if they are annealed.Ed.