Cornmeal fireforming...COW?

Discussion in 'Reloading' started by jmden, Feb 13, 2008.

  1. jmden

    jmden Well-Known Member

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    I've done some searching regarding this method of fireforming, but now I need a recipe for 300RUM size cases and haven't found a great deal.
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    royinidaho did have this to say:

    "Unique powder under cornmeal plugged w/tissue paper.
    Remove brake and don't let the barrel get too hot.
    Also, its loud....
    How much unique? For Ultra Mag size cases as much as 20 grains but you are on your own with this."
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    What is unique power and where to you get it? Is there another commonly used recipe?

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    Steve Schelp had this to say also regarding fireforming:

    "One thing that I found that helps with fire-forming brass that hasn't already been mentioned is lightly lubing the cases. This ensures they don't momentarily stick to the chamber walls and not properly setback against the bolt face. If this happens you stretch the brass walls. I use just enough imperial sizing wax to just make my fingers shiny. And then evenly apply to all cases. Swabbing your chamber every so many rounds is a good idea as mentioned above to make sure that debris doesn't stick to the greasy chamber.
    I lube my cases very lightly when using the cornmeal/toilet paper or full load fire-forming method. Have seen the evidence when I forgot to do this to 10 cases out of a batch of (100) 338 Lapua cases. Of the 10 that I forgot to lube when forming I lost 4? cases after 5-7 firings. I only lost 2 cases out of the other 90 cases after 20+ firings. Pretty conclusive evidence."

    What to folks think of this lubing of cases when fireforming? You'd have to be extra careful of cormeal/debris sticking to the walls of the chamber with sticky lube in there.

    Just trying to gather the necessary info to do this without causing any harm to myself, rifle or cases. Thanks for the input.
     
  2. royinidaho

    royinidaho Writers Guild

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    jmden,

    Yup, that's what I said. I got the recipe from Kirby and use it for fire forming the 270 AM cases from 7mm and 300 Rum brass.

    Unique is a pistol or shot shell powder.

    I use no lube.

    Ensure that you leave a little at the base of the neck unsized. I have a piece of cardboard, more that an business card and way less than the card board back of a writing tablet that I put on top of the shell holder when neck sizing.

    The last time I did it I used the process to blow the snow off of the sidewalk.:D
     

  3. goodgrouper

    goodgrouper Well-Known Member

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    I tried the lube trick as per Mike Rattigan's directions for fireforming brass and it actually made the brass not fireform as nice as dry cases! But I admit is was veeeerrrrrry cold the day I tried it.
     
  4. gunner45

    gunner45 Active Member

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    What he said...Leave a tiny false shoulder when sizing. You want a tight fit of the case in the chamber. You will know you have the right amount of Unique when the shoulder of the fireformed case is sharp and not rounded. I'm not sure how much and will defer to others on this. I used bullseye for a long time with either cornmeal or cream of wheat and toilet paper wads. Fill the case to the top with the cornmeal and compress it with the toilet paper and pack it with a pencil or something. It needs to be tight. I think it was 6 or 8 grains of Bullseye. After the first 2 or 3 cases it will come to you. I used no lube.
     
  5. Boss Hoss

    Boss Hoss Well-Known Member

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    Very Easy!! I always use the same formuls more or less. On my 300 Slowpoke which the parent is the 300 RUM just fill with 65% to 75% Bullseye and poke a small piece of cotton ball in the top to hold the powder in place. This builds up heat pretty quick so figure on 20 to 30 per hour depending on the temps outside. I use a can of air to cool the tube--turn it upside down and it comes out as a liquid at about 90 below.

    Have formed thousands upon thousands this way from 6PPC to the 338 Lapua Improved.
     
    Last edited: Feb 15, 2008
  6. jmden

    jmden Well-Known Member

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    Thanks guys, for the replies.

    Anyone else out there with experience with lubing the cases a bit for fireforming? I'm trying to think of what occurs mechanically if one were to do this. On the surface, it seems like it might help the case form better, but gg's experience (cold as it may have been) didn't seem positive. Someone else must have some fairly difinitive experience here?

    Thanks for the input. Always learning here...!
     
  7. Maico

    Maico Well-Known Member

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    Guys I ran across this thread and I thought...I've got some 22 Hornet that needs forming to K.. I found an article that said to prime the case and fill the case full of Bullseye..then weight it...divide by 10 and use the figure as your charge. Then fill with cornmeal or etc and shoot. Well the little case held 9.8gr..÷ by 10=.98grs. So I rounded it off to 1gr pack the cmeal in and poked some paper in the end...I did keep the paper wadding the same size in case that would cause a difference in PSI. Whamo they came out perfect. I had done this in the past but let it slip my mind I reckon.
    As far as larger cases I think this formula would work. I don't have anything larger to form. Somebody try it and see.
     
  8. Boss Hoss

    Boss Hoss Well-Known Member

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    I believe that is the method Ken Howell has outlined in his book. Ken and I discussed that a little last weekend when I visited him in NM. I still like to just use Bullseye but I am sure his works great mine is just easier. Speedy Gonzales taught me the "Bullseye" technique and he has done hundreds of thousands of cases this way.