Annealing and fire forming cases??

Discussion in 'The Ammo & Reloading Forum' started by LDBennett, Feb 27, 2010.

  1. LDBennett

    LDBennett Well-Known Member

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    My son-in-law and I have decided to get into a 50 cal rifle. Since we live in California 50BMG is outlawed. But the devious Californians found a way: convert 50BMG to 50DTC. It is legal because the law prohibits 50BMG not all 50 cal guns.! It's the same 50BMG case with the shoulder reshaped and ever so slightly shorter. It uses 50BMG bullets and primers. BOHICA can supply the bolt operated upper to fit our AR-15 lower we just put together . Commercial ammo, of course, is un-obtainable (???). So the cases must be fire formed to the new chamber. It has been suggest that the case shoulders be annealed before sizing in a 50DTC sizing die and fire forming the brass in the gun.

    Here is my planned approach and if anyone see something wrong please speak up. Ruining the brass at a buck a case is not cost effective:

    1) Deprime all the cases with a punch (carefully). I'll make a base on the lathe to hold the case with a hole to allow the primer to fall out.

    2) Mark the case shoulder with a 700 degree temperature crayon all the way around.

    3) Set a pan of water on a home made turn table

    4) Set the case in the pan of water vertically so that more than half of the body of the case is in the water and the case shoulder is out of the water.

    5) Using a propane torch on the case shoulder while rotating the turn table, heat the shoulder until the crayon indicates 700 degrees F is reached.

    6) Immediately tip the case over into the water to completely submerge it to cool it.

    Anyone see a problem with doing it this way?

    How much of a download should be used to fire form the case in the gun, if at all? 50BMG case wall thickness is 0.024 inches on the Once Fired brass I just bought.

    Will a propane torch do it or will I have to use my acetylene torch? I am only going to do 50 cases.

    And yes, I'll remove the primer crimp.

    LDBennett
    Last edited: Feb 27, 2010
  2. jdon72

    jdon72 New Member

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    LD,

    Talk to Gearheadpro or pyro. He is working on an annealing device. He also has videos on youtube and it is being professionally done. It impressed me. Just search his threads...there was one a few weeks ago. GL

    J
  3. LDBennett

    LDBennett Well-Known Member

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    jdon72:

    I know about the device but I only have 50 case to do. His device would be good if I did this all the time. In 25 years of reloading I have never had to anneal case before and I suspect after doing these 50 case I'll probably never have to do it again (??). But thanks for trying to be helpful.

    LDBennett
  4. jdon72

    jdon72 New Member

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  5. The_Rifleman

    The_Rifleman New Member

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    I would just use the lowest charge recommended for that cartridge.

    I use a propane torch set fairly low. I put my case in a deep-well socket on a 10 inch extension and hold the case so the blue point of the flame touches the area I am annealing. I then turn the socket apparatus until I see the flames turn orange, I then make sure I rotate it a whole turn then dump the case into water.

    Many will wait until the case glows orange but I don't heat mine as much.
  6. JLA

    JLA Well-Known Member

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    I anneal tha same way rifleman does it except I chuck my cases in a drill via the LEE trimmer stud and turn them fairly quickly while heating. this gives me an even heat, and i dont bother quenching. I believe it makes the brass brittle.

    Getting the .50 BMG chucked in a drill may be a daunting task. I dont know if LEE offers a trimmer for it...
  7. jdon72

    jdon72 New Member

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    LD,

    I just remembered that gearhead will do the annealing for you...I do not know how much he charges, but he may do yours for a promotional deal. However, it takes the fun and pride out of one owns work.

    GL

    J
  8. LDBennett

    LDBennett Well-Known Member

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    JLA:

    My understanding and experience is that is copper [and brass is supposedly 30% zinc and 70% copper (??)] becomes softer (anneals) with heating and quenching. Quenching will not make it more brittle but will freeze the crystalline structure in the soft state. Slow cooling will allow the brass to return to a harder state than annealing with quenching. Maybe slow cooling removes most of the work hardening but annealing with a cold water quench will make the cases softer. That is my understanding and what I have observed over the years when annealing copper gaskets for motorcycles.

    jdon72:

    If what I proposed is all the work I need to do to anneal cases then I WANT to do it my self for the very reasons you suggested. If the process is much more complicated then I might choose to have others do it for me.

    But thank you for the thought that the "guy" may do it for others. I did not know that. I thought he was just going to sell the machine when he got it done(???).

    LDBennett
  9. Gearheadpyro

    Gearheadpyro New Member

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    LD:

    Your process is pretty right on, except you don't need to quench brass. Quenching steel will affect the crystal structure. Quenching brass does nothing but get the case wet.

    750F or so is about as hot as you can get it without making it too soft, 700F is a good target.

    Try to turn the case fast enough to keep the heating even, the big key to annealing is consistency. If you have access to a power screwdriver try chucking a socket that closely fits the case and using that to turn it.

    Once I have my machine (I.C.A. 2000) built I will anneal other's brass if they would like, but it is not running yet. I do also plan to sell the machine, however, it will not be able to handle the big 50's. Due to the nature of the induction heater I will use the work coil will need to be close to the case. If I build the machine to work for the big 50's it will have difficulties with the far more popular .223's.
  10. howlnmad

    howlnmad Well-Known Member

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    Yep, they do. Midway has one listed for 14.99.
  11. JLA

    JLA Well-Known Member

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    Thanks LD, I did look into that since posting here last. Next go round with annealing ill quench and see how it goes.
  12. LDBennett

    LDBennett Well-Known Member

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    JLA:

    In an old article from the 1950's the writer points out that you can not allow the base of the cartridge to get any heat at all or it will be so soft that it will loose its required strength. That is why you stand them in water. If you allow them to air cool as suggested by some, the heat from the shoulder will eventually get transfered to the base and MAYBE effect it (??). Quick cooling by tipping the heated case over into the water assures that the shoulder heat never gets to the case's base.

    LDBennett
  13. Gearheadpyro

    Gearheadpyro New Member

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    LD,

    Brass changes its crystalline structure (softens) at around 450F, if you apply enough heat quickly enough to the neck area you will never get the base up to that temperature. Annealing a case should only take a few seconds regardless of the method used.

    There is nothing wrong with standing the cases in water to prevent heat transfer, it's just not essential.
  14. JLA

    JLA Well-Known Member

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    I think ill just keep doing it the way i do it. I can touch the base after annealing, thats how i get it out of the trimmer stud. then I stand them up in a plastic loading block and it doesnt melt. Thatll save me from having to wait til they dry to proceed... Thanks gearhead and LD.. Hey gearhead, hows that case annealing inductor thingy going? been awhile since i looked it up. Any new developments since the timer???
  15. Gearheadpyro

    Gearheadpyro New Member

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    Lots have happened since then, JLA. I've got a new induction heater in that costs only 1/3 of the Mini-Ductor, but I haven't fired it up yet. I'm waiting on a few more parts for that.

    I've been controlling the heater with a micro-chip that I flash a code on.

    I've made a lot of progress on automating it, but am not there yet. I've had several major setbacks in automating, but it's in the works. I've got lots of updates and pictures on my blog if you want to check it out.
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