Chemisrty Book Annealing

[crashresidue]

Cheers,

If you've followed the "YO - The Shrink" postings - well - "Grumpy" called back.

Here goes: cartridge brass is an alloy of 30% zink and 70% copper.  The zink can differ + /- 1/2 %.  

To anneal the "total" cartridge stand cartridges in a pan in an oven and bake for one hour at 500F.  That's one hour a 500F, not including heat-up time.  Use an "oven thermometor(sp?)."

If the cartridges show "excessive oxygenation", then bury in a 50/50 mixture of sand and powdered charcoal.  Bake for one hour at 500F - not including heat-up time.

"Excessive oxygenation" is discoloration of the brass - I don't know if this hurts the brass, but I guess it must if they gave a "cure" for it.

I've just gotten off the RCBS web page and asked them what they think caused the cracking I've seen and how they recommend annealing brass.  Guess we'll find out one way or another.

cr

[HWooldridge]

Here's another way.  Put cases in a pan of water with the top 1/3 sticking out of the water.  Heat each one with a regular old propane torch until blue and then tip the case into the water.  Copper alloys are softened by heating and quenching, which is the exact opposite of carbon steel.  If you don't have a propane torch, you can do the same thing by putting them in the oven, heating to 500 degrees for 5 minutes and then dumping the whole thing into a pan of water.

[John Traveler]

Putting your cartridge cases into an OVEN is a graranteed way to ruin the entire case for reloading!

That cartridge case head needs to remain relatively hard and "springy" to work properly.  If you heat the entire cartridge case, you will draw the temper of the brass where it NEEDS to be hard to withstand pressure.  Specifically, your primer pockets will tend to loosen, and you will get more base expansion than normal.

Now, granted, for blackpowder pistol cartridge use, the hardness of the cartridge case may not be all that critical, but at rifle pressures, it is likely to make you unhappy!

One of the old-time rules for determining when your cartridge cases need annealilng is simple:  squeeze or pinch the case mouth hard, and if it resists, tap two case mouths together.  The soft cases will give a dull "tink" and the too-hard cases will "ring" with a distinctive bell-like sound.

[crashresidue]

Cheers,

Thanks John - I was sort of that opinion myself - but "Grumpy" makes "no" mistakes - just ask him!

I'll give RCBS time to answer - but I anneal with the propane torch and water just like everybody else.

Either I've been around turbine engines too long - or I've got a bunch of brass that's going to get "hot" tonight.  They all seem to "ring" to me.

cr

[John Traveler]

Oh, by the way, while I have no doubt that there IS a term called "excessive oxygenation"  or burning, where brass discolors from heating, I dunno if it applies to cartridge brass.  the burning referred to means that zinc has separated from the alloy and lost due to oxydation.  Cartridge brass alloys DO vary, depending on what caliber the ammunition is.  Small arms, medium auto cannon, or large artillery uses different alloys.

Commercial brass cartridge case manufacture involves a flame anneal step (SURPRISE!!) where each case is exposed to a gas torch flame.  The anneal produces the bluish-brown discoloration seen on the neck and shoulders of military rifle cartridge cases.  The military specification requires that the discoloration be visible, and not removed by polishing.  Such annealing is required for long-term stability of case necks (with bullets held under tension) that may be subject to cracking when in storage.  It is common to see much loaded ammunition from before the 1930's and 1940's that have cracked case necks.

Commercial cartridge cases, while annealed the same way and have the same discoloration, are tumble polished to remove the discoloration.