COW fire forming

Discussion in 'Reloading Forum (All Calibers)' started by Alex Wheeler, Oct 14, 2018.

  1. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    There are a couple reasons I do not like or recommend cream of wheat or any other filler type fire forming. One is simple, walnut shells can be used as a sand blasting media, think about that. Second is how we are forming the case and how the forming differs. When you fire form with a bullet and powder you essentially have a pressure vessel with pressure forcing the case outwards in all directions. This why cases shorten up when formed, they are pulling brass down into the shoulder. This is the correct way to do it IMO. With cow you are compressing a media under high pressure and then forcing it through the neck, pulling the neck forward stretching the shoulder brass. What I want to see in a formed case is 2 things. I want the case to shorten, and I want the oal variation to remain the same as virgin cases or close to it. If new brass has a .003" variation short to long, I want to see .003" variation after ffing as well. If you end up with .010" variation for example, you have not formed cases in a consistent way.
     
  2. ARK

    ARK

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    Do you fire form with the same bullets you are shooting or - say - less expensive ones?
     
  3. sdean

    sdean Silver $$ Contributor

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    Alex Curious your thoughts on hydroforming.
     
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  4. Uncle Ed

    Uncle Ed

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    I fire form my cases using the COW method, BUT inserting the brass into the chamber and then finding the brass afterwards can be a problem. And you have to wet tumble the cases immediately or else they turn green. :eek:

    [​IMG]
     
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  5. C.E.Smith043

    C.E.Smith043 Gold $$ Contributor

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    lol...i love you. You always make me smile, and have been for years
     
  6. shortthroat

    shortthroat Silver $$ Contributor

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    I fire form with Thompson Contender using hard cast lead bullets and 3 gr. bullseye. For 6.5 grendel that gives a very mild load. I put the grandson to work on the job and he gets a nice group at 25 yds. and I get nicely formed brass from 7.62x39.
     
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  7. Ledd Slinger

    Ledd Slinger Gold $$ Contributor

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    I agree with using bullets for FF. I used the COW method one time and my case forming dimensional results were very inconsistent. Fire forming with bullets gives excellent results.

    Even the best barrels usually takes 50 to 100 rounds (depending on quality of lapping finish) before you start seeing "consistent" results during load testing and tuning. This is why I am a big advocate for barrel break in procedures and using bullets for fireforming. Being that I personally will not trust a barrel to deliver consistent load testing results until it has around 50-100 rounds fired, I use this time to fire form brass as I sight in and get elevation drop values. Will also use fire forming period to conduct scope testing on optics. The formed cases are then used for load tuning. I fireform the remaining new brass over time as fouler and sighter rounds and set them all aside so they are ready to go as once fired cases when they are needed.

    Not saying it's the best way to do business, it's just how I like to do it.
     
    Last edited: Oct 15, 2018
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  8. 6MMsteve

    6MMsteve Gold $$ Contributor

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    I quit cow also, messy and I don't shoot that much, so I'm not going to hurt my barrel
     
  9. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Its my preferred method.
     
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  10. earlcurtis67

    earlcurtis67 Silver $$ Contributor

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    But you should still fire form to the chamber for best results?
     
  11. LA50SHOOTER

    LA50SHOOTER Gold $$ Contributor

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    Alex, - C.O.W. is Not Walnut shells (as we all know) - but no doubt there is some "abrasive" effect of C.O.W. - exactly how much is another story, but surely not as much as Walnut Hulls. - Powder does also have an "abrasive effect" as it burns.

    - Not saying that a bullet seated to, or into the lands is not a "correct" or effective way to fire-form. (at all).
    I've fire-formed brass from .223 to 223 A.I. all the way up to 50 bmg to 50 bmg Imp. and in some instances I've used C.O.W. as a filler & also a wax plug, along with a "false shoulder" turned into the neck.
    And the cases did shorten and it was consistent. - I believe that type / burn-rate of the powder being used and the amount of it has much to do with the out-come when using C.O.W. as a fire-forming method.
    - I don't "advocate" C.O.W. fire-forming as a means to all ends or "the best method" ever created. - I do believe that it can be used effectively to form brass "to a partial degree" to where on the next (2nd) firing there isn't headspace concerns in the brass length (case head to datum).

    To me what you've stated (in regards to C.O.W. and its use) has some inconclusiveness in it in reference to using C.O.W. as a fire-forming method.
    - Also, how do you know where the brass is coming from and where its going to during the fire-forming process when using C.O.W. ??
    - And how do you know how much pressure is being built in the process. And if a wax plug is used how much does the pressure differ versus using a bullet seated say 0.010 into the lands ??

    Not trying to stir up a hornets nest here, I just believe that there is a "way" to use C.O.W. to fire-form partially & if done correctly decent results can be obtained, there are other articles on here and on the accurateshooter.com website that substantiate using C.O.W. as a "method" to form brass.

    I use it (C.O.W.) when the parent case dimensions in the body length are shorter than the body length dimensions of the finished cartridge. And as a method to get the body length correct.
    - On a "true" Ackley Improved cartridge the Ackley versions body / datum to case head dimension is normally 0.004 LESS than the non-improved parent case (chamber dimensions) so in essence that is not normally problematic and a bullet seated at any "reasonable length" works fine, provided the brass being used doesn't have head-space issues from the start. (As the Ackley version is actually 0.004 less - datum to case head)

    - Ron -
     
  12. SPJ

    SPJ Silver $$ Contributor

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    I prefer rifle powder in my rifle and breakfast cereal in a bowl.
    Just me of course
     
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  13. LA50SHOOTER

    LA50SHOOTER Gold $$ Contributor

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    And you don't pay +2 dollars per bullet in your rifles either.
     
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  14. LA50SHOOTER

    LA50SHOOTER Gold $$ Contributor

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    Also, - I DON"T advocate using C.O.W. for everything that needs fire-formed.
    - Most Ackley Improved chambers do pretty decent from an accuracy standpoint with a bullet & a decent charge of the right powder. - There are some instances that C.O.W. has a place in "my" loading regime.
     
  15. butchlambert

    butchlambert Site $$ Sponsor

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    I use powder and a wax plug. No abrasive unless wax is full of grit. Growing .002 in length ain't a problem. I do have fireforming barrels.
     
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  16. Link

    Link Silver $$ Contributor

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    I would also like to know what bullet to use in fireforming and fowlers. I use the cheapest I can find, hope that's ok/
     
  17. butchlambert

    butchlambert Site $$ Sponsor

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    I use bullets in my 280AI, but cheap ones. No reason to use good ones.
     
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  18. SPJ

    SPJ Silver $$ Contributor

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    I use culled out Bullets
    Agreed with Butch ^^
     
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  19. Baddog0302

    Baddog0302 Silver $$ Contributor

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    Just a thought, use a low cost bullet and seat it long so the case head is pressed firmly against the bolt face, or but using a mandrel or a tapered expander ball to open the neck up to one caliber larger that the case was originally , then re sizing the neck only enough so the case will chamber with some effort, thus forming a false shoulder, in either case the case bode has less chance of stretching and weaking at the web.
     
  20. SPJ

    SPJ Silver $$ Contributor

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    Just curious here Ron
    Have you tried gun powder and a 100% cotton ball?
     
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