A group of us are discussing the use of Lathe turned brass cartridges. While most agree that Drawn brass can withstand much higher pressures than Lathe Turned 360 Brass cases, there is little direct experience outside of low pressure black powder rounds such as the 45-110 and 50-110. What experience if any is there with Lathe Turned brass for the larger British rounds such as the .600 NE or .700 NE. Rumor has it that A-Squared warned against the use of such cases, but it's unsubstantiated. Most articles do not directly address this issue. We believe that 38KPSI cartridges would be safe with Lathe Turned Brass.We would appreciate the experiences of those on this forum who may be able to shed some light on this.-Rob

Rob, I gust spoke with Dave at Rocky mountain cartridge company. He truns brass for the black powder guys. He feels that 38K is max for any turned 360 half hard brass case. I think we've barking up the right tree.
John

I just talked to Butch Searcy and he has used Lathe Turned brass on both the .600NE and 700NE and confirms that 38Kpsi should not be a problem at all.-Rob

I've been using the LT brass from RMC for my .577 Snider and it works well. However, I've been keeping pressures down to around 28Kpsi. This is not because the brass might not be able to handle it, but because the gun itself is 130yrs old.

However, I've always heard 38Kpsi for LT brass.

Cold formed brass will have a fibered microstructure which will handle the hoop and tangential loads much better. If the lathe work is not done exceptionally well, you could have tool marks, sharp corners (radii), and non-concentric dimensions, which result in a higher stress concentration factor.
Hate to agree with A-Square on a lot of topics , but their advise to avoid this type of case for high pressure loads probably is good advice.

Brass is sold as type and I assume you would get cartridge brass, 70Cu30Zn.and hardness. Fullhard, half hard ,quarter hard, annealed.The hardness differences are very significant. And as paul mentions ,cold formed brass has a better microstructure. I would do it for black powder pressues like 45-70 27,000psi with half hard brass but wouldn't push it beyond that especially if its an old gun.

From Dave Casey of Rocky Mountain Cartridge:

"The turned brass cases I make are for the old obsolete black powder and early smokless loadings. Most of these chamberings are 35,000 CUP or less. Also for cast lead target loadings, as the pressures are in the same range."

I spoke to Dave Casey awhile back and he said the same as he told Nick.

True brass cu/zn does not have a "fibered microstructure" under any circumstance.

Incidently MSC is Haveing a sale for 360 brass round stock for this month (Dec).

I know brass behaves differently from steel. Steel is hardened if heated and quenched, whereas the same process anneals brass. Is there a heat treatment for brass that would make it hard enough for case heads?

How about steel and aluminum? Would they end up hard enough machined, or do you need to stamp these to turn out a hard enough product?

H. C.

HenryC470 Like many silver alloys... you can "heat harden" most true brass. This however takes knowledge that is not common to most. The what you are doing when heat hardening is allowing dislocations and vacancies in the atomic lattice structure to move/be filled into a more uniform matrix. Understanding how much heat and how long... gets realy silly. It is not like holding a torch, and temps are kinda low. My understanding to this is quite limited, ill have to ask one of my teachers.
By heat hardening... you do not reach hardness levels you would by work hardening. One Idea to lathe turned brass is to do your turning, then make a set of burnishers to go over the brass while its in the/a lathe. This will not only take tooling marks out but will also harden the surface from cold forming.

[ 12-22-2002, 10:26: Message edited by: smallfry ]

Most brasses are not heat treatable, though some special types can be hardened by precipitation. Burnishing to harden would be very difficult to control.Forged brass will improve properties though the term fibre microstructure is not correct. Cases are made by back extrusion. Typically there are a series of extrusion and annealing steps to make a case with particular attention to hardness and grain size. Properly done you may have different hardness in different parts of the case. Control of grain size and texture and hardness are not nearly as controlable with machined brass.Much brass rod is a free machining grade which I would not use.