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My nicely cleaned but wet 8mm Mauser cases had been drying in the oven on a nice low temperature when, unknown to me, my wife decided to wack it up 240 degs in order to put the joint in.

The cases had been cooking for about 25 mins before I could rescue them. The cases had darkened a little with a hint of cherry red. Would it be wise to scrap them due to some sort of metallurgical harm, or are they safe to use as before?

Please, no lectures on distraction and carelessness. It was my fault really and a lesson learned with an upset wife to contend with at the same time.

You have annealed your cases. The problem is that you have annealed the whole case, including the high pressure end and this is not recommended, especially on a fullbore rifle case.
I would scrap them.
Fred

Pretty much what I thought. Thanks for confirming it. I must admit I thought annealing involved a blowtorch but I'll err on the side of caution. Cheers, David

Definitely scrap them, cases can be replaced, fingers and eyes can't.

ukrifleman

I wouldn’t use them for a full pressure load, but I’d be tempted to keep them and use them for gallery loads.

Possibly Not.

You have stress relived the case bodies but not annealed them. Annealing i.e. the recrystalisation temperature for 70:30 cartridge brass starts at 450C & is best at nearer 650C, stress relieving starts at 250-350C. The hardness of the case will not have changed by much so the base tensile strength of the metal will have reduced but not by much. The crystallographic structure will not have changed.

The tarnishing is heat oxidation of the copper in the brass its superficial.

got a thermocouple? put it on a case & measure the actual temperature where the cases were? I bet it was lower than 240C (gas ovens tend to be lower esp if its a fan oven) but they tend to over heat first so the profile will be warming up to say 280 then cooling back to 220 for most of the duration of the 25 mins.

..........so my advice would be - make 10 cartridges to 2% below your normal load & test them. (if you get any signs of case body separation ditch them) if they eject OK use them but not with high end match rifle or 1200 yd loads.

Phil
HND Metallurgy, BSc (Hons) Materials Science & Tech :-)

Personally, I wouldn't want to risk it because I'm not an expert (but luckily hitchphil has offered some good technical information :) ). If the case fails, then it would very likely be at the case head where the primer is inserted.

How many cases were cooked? If its a handful, just toss them in the bin and think nothing of it.

Does your rifle have a gas vent on the side of the chamber? The Lee Enfield has a gas vent on the side of the chamber so in the event that your case ruptures the gas is safely vented through this hole and not into the shooters face. My Yugoslavian Mauser does not have this vent, so when I fired some underpowered (factory) rounds which did not obturate, the cool gas blew back through the action into my face. Assuming your rifle is a Mauser kar98, then bear this in mind in the event that the case fails.

Where my post go???

snayperskaya wrote:Where my post go???

............... have you done enough meaningful posts to be allowed

Soviet propaganda on brass annealing techniques are not welcome in capitalist UK