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Thread: Annealing Jackets

  1. #1
    Boolit Master
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    Annealing Jackets

    Ok, let's do this again.

    The title says Annealing Jackets. This includes fired brass cases to be used as bullet jackets. We are not discussing annealing necks for cartridge reloading.

    It is important to anneal bullet jackets for best performance. No commercial bullet maker bypasses this step, and in fact some commercial bullet jackets are annealed more than once. When dealing with fired cases as jackets, this is even more important. You have no way to know how hard or soft any case is compared to another. Annealing puts all of the cases into the same condition.

    Jackets need to be soft enough to engrave properly, and deform into the rifling grooves in the bore to make an effective seal. The head of a brass case that has not been fully annealed may not fill the corners of the rifling, and can give poor results. Hard jackets also increase the stress on die parts and press components, shortening the life of both.

    Annealing Copper and Copper Alloys

    Much misinformation exists in the firearms world regarding annealing copper & brass. Copper and it's alloys are metals of a face centered cubic structure that work hardens easily. As copper is moved or worked, the crystals are displaced or dislocated in relationship to each other. Annealing it requires raising the temperature high enough to allow the crystals to realign.

    The minimum temperature required to properly anneal copper and it's alloys is easily calculated. Face centered cubic metals begin to anneal at just over half the absolute melting point. Sounds simple enough pure copper melts @ 1356˚ Kelvin, so half of that would be 678˚ K or 405˚ C about 761˚ F.

    That is the minimum temperature for annealing pure copper. If you were to leave copper to soak at that temperature long enough it would become fully annealed. Nobody wants to wait that long. Raising the temperature reduces the time it takes to anneal. In an industrial environment, copper annealing usually takes place between 700˚C (1292˚F) to 900˚C (1652˚F). An average (85Cu 15Zn) Brass has a melting point of slightly less than copper (1213˚K), and a proper annealing range should be 650˚C to 725˚C for a short period of time. Because brass is a zinc alloy, heating times should be short to keep the zinc in the alloy.

    As a frame of reference, Aluminum melts @ 659˚C or 1218˚F. If your heat source does not melt aluminum, it is not hot enough to anneal rapidly. If your heat source does not reach 750F, it will not anneal copper at all. Most kitchen appliances are not up to the annealing task, and should not be considered for this type of work. An inexpensive propane torch & a firebrick are a much better choice for annealing cases & jackets.

    A word about quenching. Copper and it's alloys do not need to be quenched after heating to anneal. Quenching can reduce the oxidization, but is not part of the annealing process. Quench, air cool it makes no difference to the copper or brass.

    Some of you guys have self cleaning electric ovens. With a peak temp of 900˚F or so, and a cycle time around an hour, that should do just fine for annealing large lots of brass. A toaster oven will not do the job.

    B.

  2. #2
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    annealing 308 brass jackets in Wood stove and clean with a Citric acid bath

    I begin by cutting used 5.7x28 cases to the length I need.
    I use a Mini-chop saw from Harbor freight to cut.
    I touch the blade with some beeswax boolit lube
    about every 6 cuts for easier cutting.



    The cases, just cut, go into a stainless collander.
    Do not over fill the collander, one layer is just right.
    about 100 cases, it goes quick...4 or 5 minutes.



    I arrange the red coals, then add a small piece of wood.
    I found the flame anneals them quicker, but a large flame
    will melt them. Watch closely.





    there will be hot spots, stir them around to rearrange the cases,
    so they all get to glowing at some point.



    Once they are fully annealed, let them cool-fast or slow, it doesn't matter.
    For safety reasons, I drop them in cold water.
    Then I put them into a nylon laundry bag and put that into a old
    crock pot with my Citric acid bath cooking away.
    (3 tblsp pure citric acid powder into 1 gallon water).
    I leave them in there for 5 minutes.
    then I rinse them at least twice.



    Then I partly dry them on a towel.


    I dry them the rest of the way on the wood stove,
    or outside in the sun if it's summertime.
    or an oven works too.

  3. #3
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    And they stay that bright and shinny days later? Man I should show you what mine look like after a few hours after my acid bath. I don't dry them off soon enough apperntly (Ok I didn't dry them at all, just pored them on a towel) or it is the difference between the pool ph reducer and your citric acid bath because mine go from bright and shiny to ugly tarnished look in a few hours. Then it is 8-12 hours in the tumbler getting them clean again.

    Great pics and advise though. Thanks for posting it. I use the exact same stainless steel colender but I don't have a fire place. I did line the inside of my BBQ with fire brick though and now it getss real hot. I'll try and post some pics too. I annealed 5 gallons of 9mm and 5 gallons of 5.7 over the weekend and the tumbler has been on 24-7 ever sence.

    If your brass stays that shiny with out tumbling I will for sure be picking up some of that citric acid.

    Thanks Jon,

    Swage On!

    BT
    Last edited by BT Sniper; 01-26-2011 at 04:41 PM.
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    Good shooting and swage on!

    Brian

  4. #4
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    I like the nylon bag idea! After rereading it a couple times I don't think we could make it any simpler without a kiln, at least you get the benifit of warming your house.

    Great post!

    Thanks B and Jon, this should really take care of any issues about annealing brass for jackets. Really can be very easy and fast.

    Good shooting,

    BT
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    Check out available BTSniper products and prices at
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    Good shooting and swage on!

    Brian

  5. #5
    Boolit Master
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    Very nice, Jon B. Thanks for taking the time to post that.

    All that oxygen will get rid of that polymer coating quick!

    Brian:
    Now you know why I kept saying pool acid should stay in the pool shed.

    Citric acid does indeed passivate brass. Thanks to the other thread, there are lots of references to both suppliers of citric acid, and processing methods.

    B.

  6. #6
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    Yep! I'll look into it. I may just agree to keep the pool acid in the pool too!

    Great job guys. I did take your addvise on the fire bricks, nearly able to turn the BBQ into a kiln now. I'll have to take some pics soon.

    Link to other thread on passivating brass with citric acid?? I'll find it soon enough but should one of you wish to make it easy for us, Thanks!

    BT
    Last edited by BT Sniper; 01-26-2011 at 04:43 PM.
    When you stop learning you are dying.

    Check out available BTSniper products and prices at
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    Good shooting and swage on!

    Brian

  7. #7
    Boolit Master
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    Here ya go BT http://castboolits.gunloads.com/showthread.php?t=83572

    Its a sticky in the kit room

  8. #8
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    That is a loooooooooooooong thread.
    Sagacious really knows his stuff, that's for sure.

    Check out Post 215 through 220 on page 11.
    summary is, once the citric solution starts turning blue,
    it loses it's strength, but if you then dip a clean piece
    of steel in it, it will copper plate it...Far out !

  9. #9
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    TNX! I'll check it out.

    BT
    When you stop learning you are dying.

    Check out available BTSniper products and prices at
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    Say hello and like my FB page as well.
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    Good shooting and swage on!

    Brian

  10. #10
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    Well I asked around about how to anneal and from what I read I thought I did not have anything to do it with handy. I was thinking a fire would be to much and end up with melted brass. Super post wish I sent it sooner. All that being said this is what I came up with I am still fine tuning it but it takes about 20 sec to turn one red.
    http://
    I think I will retire it and go with the SS basket and a fire looks alot easier and faster.
    Reloading to save money I am sure the saving is going to start soon

  11. #11
    OK...silly question...can I take a pile of my rimfire brass...put them in my Dutch oven...use my gas plumber's furnace...and anneal them without over doing it?

  12. #12
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    I borrowed an electric kiln from a friend and did 400 .40 S&W brass, with lead cores, the other night in about an hour, including warmup time for the kiln. I took them up to 1200 degrees and then let them cool. While they were cooking, I was able to do other stuff. What a breeze!

    This sure beats holding them in the flame of my propane torch three at a time....

    Hope this helps.

    Fred

  13. #13
    Boolit Master
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    Quote Originally Posted by Ammosmith View Post
    OK...silly question...can I take a pile of my rimfire brass...put them in my Dutch oven...use my gas plumber's furnace...and anneal them without over doing it?
    Sure. It is hard to calibrate the temps you can reach with that kind of setup - but not impossible. I would recommend a couple of dry run tests to see what sort of temps you are getting. Then you can work out the timing to heat to the center of the mass of cases.

    Start with the dutch oven clean inside. Place a couple of rimfire cases in it. Place a small ball (about 1/2 inch) of plain old aluminum foil in the pot too. Put the lid on & fire the pot.

    Start checking the condition of the brass & aluminum every 10 minutes or so. Run for 30 minutes. The brass should be glowing brightly. Is the aluminum melted? When did it melt?

    If the case melts, you are way too hot. If the aluminum melts, you are plenty hot. If the aluminum melted in 20 minutes, that is the time to use. Fill it up, burn for 20 minutes - shut it down & walk away while it cools.

    If neither melts, run a full batch of cases for 30 minutes, then let them cool with the lid on. Check cases from the edges of the pot, the top, bottom & center of the batch. Squeeze the case mouths with your fingers.

    If you think one from some part of the batch is harder or softer, test it against another case from the bottom. Lay both cases down on the edge of the bench so the case mouths are together. Squeeze them against each other. They should distort equally. If one crushes but the other stays round, you need to heat longer.

    If you need to re-run a batch of cases longer it is not a big deal, they only get so soft. Once you work out a run time for the dutch oven & burner full of brass, you are set.

    B.

  14. #14
    Boolit Master bearcove's Avatar
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    I have a programable Even Heat Knife oven, for heat treating. If shipping was cheaper I could run batches. If anybody is in albuquerque nm area?

  15. #15
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    Interesting offer there, shipping doesn't have to be that much. USPS flat rate box for $10-$14 can hold 3-4K worth of brass. Might be worth it to some one here. Even covering the cost of shipping both ways is cheap but man, how long do you think it would take you to cook 3 thousand cases and what would you charge? I'm good at the moment but there are those out here I bet might be interested.

    BT
    When you stop learning you are dying.

    Check out available BTSniper products and prices at
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    Good shooting and swage on!

    Brian

  16. #16
    Boolit Master
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    That is a very nice offer Bearcove.

    I usually put all my future jackets in with the 17-4 when I am running the age oven. It actually helps, since the brass mass helps keep the oven stable.

    B.

  17. #17
    Boolit Master bearcove's Avatar
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    I guess if I made a basket to fit I could do 3000 in one batch. Other than that its just soak time in oven, It will go up to 2200 deg F in about 10 minutes. 800 deg f is easy. I think the oven is about 10"h X 12"w X 19"deep inside.

    I don't know about cost. I am interested in doing some swaging but don't have a source of brass. That has kept me from starting. I would concider doing it for brass in trade.

    Then I'd have to start building a press and get my lathe set up so I can make dies.

  18. #18
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    Yep thats what I would do! Anneal people's brass in exchange for a portion of the brass when done. Thought about it a few times myself actually but never offered. It certainly isn't hard to obtain a lot of brass by severial means. There is a lot out there ending up in scrap yards that could be bullets instead.

    I don't know about annealing large lots (500 or more) at same time? Would it make the outside well done and inside medium rare? I do know we can cook the zink right out of the copper/brass cases. I suppose the correct temp over the right amount of time to cook them all evenly would be possible?

    BT
    When you stop learning you are dying.

    Check out available BTSniper products and prices at
    http://castboolits.gunloads.com/foru...?114-BT-Sniper

    Say hello and like my FB page as well.
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    Good shooting and swage on!

    Brian

  19. #19
    Boolit Master bearcove's Avatar
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    A 1000 would probably just be a layer an inch or so deep depending on size (pistol like 40s&w). 3000 22lr would not be much of a load. My oven has heat elements all the way around except the door. It would be back up to temp in a few minutes. If there is anyone interested I'd work out details with them. Once the oven is running it it would be easy to do smaller batches. You guys would know better than me. I've never annealed the whole case, just necks.

  20. #20
    Boolit Master
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    Bearcove:

    The answer you seek is "bread pans".

    When I am running 17-4 to the H900 condition, I fill the open space in the furnace with bread pans full of jacket material. A lot of 22 rimfire fits in a loaf pan. Since the steel parts age for a few hours, everything is at full anneal.

    Look through the thrift shops or junk stores for steel pans that fit your needs / kiln. A 9x12x2 baking pan will do fine if it is steel. If you use a coated pan, you will be burning off whatever is on it - and that can be pretty nasty. I avoid the coated stuff, and use plain old tin plated junk - nobody want that stuff anymore anyway. Cast iron works well too.

    If you run up to 900 ~ 1000 F, about 10 minutes per inch of depth is usually plenty of soak time.

    B.

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