Interesting finding re: case wall thickness for .223

Discussion in 'The Ammo Can' started by mongoose33, Sep 24, 2008.

  1. mongoose33

    mongoose33 XDTalk 2K Member Founding Member

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    After the discussion in other threads about the cases for .223 military brass being thicker, and thus producing lesser volume in the cases, requiring smaller loads, I decided to take some brass apart and see what was what.

    I think you'll be surprised at what I found. I was.

    Five brass casings: R P 223 Rem, FC 08, Winchester .223 Rem, FC 223 Rem, and LC 04.

    Hopefully this will come through well--sometimes tables don't work so well in posts.

    First. after depriming and trimming to length, here are the weights, in grains, of the five cases:

    RP223Rem: 91.5 gr
    FC 08: 92.1
    Winchester .223 Rem: 96.3
    FC 223 Rem: 91.5
    LC 04: 92.3.

    The heaviest casing was, oddly, the commercial Winchester brass I just bought last week and fired once.

    Second, I cut off the necks, producing a "cartridge" 1.25" long. After removing the burr, I then used a dial caliper to determine casing wall thickness at that length :

    RP223Rem: .012"
    FC 08: .012-.013"
    Winchester ..223 Rem: .012-.013"
    FC 223 Rem: .013-.014"
    LC 04: .012-.013"

    Then, I cut the cartridges down again, leaving them 1/2" long.

    I measured the casing wall again at that length, after removing any burrs:

    RP223Rem: .027"
    FC 08: .025"
    Winchester .223 Rem: .030"
    FC 223 Rem: .025"
    LC 04: .027"


    What's the upshot of all this? The conventional wisdom is that military cases are thicker, resulting in a smaller volume within the case which will, for the same amount of powder, produce higher pressures.

    But what I see is that the commercial cartridge casing, the Winchester, is the thickest of all, resulting in the smallest volume w/in the casing.!

    Can anyone shed some light on this? Obviously, the samples are small, but shockingly different than what we'd expect if the conventional wisdom is true. It sure looks to me like there isn't all that much difference between the cartirdges. (And yes, I did one of each kind, not a large sample).

     
  2. Edubya

    Edubya XDTalk 500 Member Founding Member

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    Interesting. Next, use water volume to check which has the most volume. Simply fill each trimmed case with water and then weigh the amount of water. Liquid is used because it fills all voids.
     
  3. mongoose33

    mongoose33 XDTalk 2K Member Founding Member

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    I'll have to figure out something to use to stop up the flash hole. I'm slightly skeptical of using water; I'd need to ensure there are no bubbles left behind that displace the water.

    Something with a lesser surface tension, I'd think--maybe alcohol?
     
  4. T.J.

    T.J. Official Site Vendor Supporting Vendor Founding Member

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    dont deprime it that will fill in the flash hole or fill the primer pocket with the end of an eraser cut to fit tightly. you might also be able to use elmers glue but you risk it expanding in the primer pocket and takeing up some of the case volume, yet another option yet probably a PITA is cut small pieces of tape and push it againt the primer pocket.


    also for the most accurate testing you really need to use brand new brass for all or atleast brass that you know have been fired the same amount brass is pretty soft and tend to elongate which result in the case walls getting thinner as it stretches,

    given that the thickest was unfired brass it would stand to reason that since it had not been stretched out that the walls would be thicker.
     
  5. mongoose33

    mongoose33 XDTalk 2K Member Founding Member

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    I'll have to deprime them. I want them all cut to the same length.
    All of it is once-fired, so far as I know. Collected either from what I shot handloads from new Win brass, or collected from a police range where I don't believe anyone is shooting reloads.

    It was once-fired. I know, because I fired it. :)
     
  6. agalindo

    agalindo XDTalk 15K Member Founding Member

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    Case weight will vary by lot number even withing the same manufacturer so a WW case of a different lot will weigh a bit different that what you have now.
     
  7. T.J.

    T.J. Official Site Vendor Supporting Vendor Founding Member

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    thats easy enough just put the dead primer back in after each cut. but if you are just going measure capacity using liquid why cut them just use your chamfer tool until they are the exact same length.
     
  8. Hillbilly Jim

    Hillbilly Jim XDTalk 100 Member

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    Mongoose
    I have found the exact same thing when weighing brass. Using once fired brass not trimed gave me the same results as your research. I didnt think it was worth the trouble to fill with water and weigh, just loaded and shot.
    Hillbilly Jim

     

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