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what are fluting ridges?

Discussion in 'Ammunition & Reloading' started by james2562, Apr 29, 2012.

  1. james2562

    james2562 Kent Member

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    There is a guy selling 308 brass. the add says "pieces were shot through a port-buffer equipped PTR-91 so the cases have fluting ridges"

    two questions:
    how are fluting ridges caused?

    what is the significance of fluting ridges?
  2. DieselScout

    DieselScout S Clackamas County Well-Known Member

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    Some semi auto battle style rifles have fluted chambers to help with extraction. As the brass expands as it fired it expands into those flutes leaving ridges on the spent brass. I don't know if this has any effect in reloading or not i have never had any experience with the spent brass.
  3. Mark W.

    Mark W. Silverton, OR Bronze Supporter Bronze Supporter

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    This is from RCBS on this subect:

    Reply from RCBS my thought would be to not use the brass for reloading. My
    reasoning is that most often the rounds were fired in a H&K semi-auto or
    full-auto firearm (or para-military look alike). The flutes in the
    chamber are to ease the extraction forces of the hot case and lessen how
    tight it adheres to the chamber wall, that puts stress on the brass at
    each flute. That sort of stress is not seen in a normal chamber since
    they don't have the flutes and to what extent that will effect case
    performance and longevity are an unknown.

    Case preparation will take time in that each case will need to be sized,
    trimmed to length, primer pocket swaged (most likely with military
    cases) and then fireformed to remove the flute dents. The amount of
    reloads available after that is an unknown and if a case fails it would
    most likely not be at the normal web-failure point, but rather at a
    flute. Case failures and escaping gas at 50,000 psi is not a good thing
    to have happen.

    My suggestion would be to take a hammer, crush each case and sell as
    scrap brass. Take that money and buy new 308 Winchester brass.

    Shoot Straight!
    Coy Getman
    2299 Snake River Ave.
    Lewiston, ID 83501
    Sr. Technical Coordinator
    (866) 286-7436 ext 5351

    I would suggest that if the brass was Mil surplus you might get away with a couple three reloads if commercial less. And the failure would not only be hard on your chamber but could be dangerous.
  4. james2562

    james2562 Kent Member

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    Thank you mark.

  5. PhysicsGuy

    PhysicsGuy Corvallis, OR Resident Science Nut

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    Also I have noticed that a lot of the surplus ammo out there uses berdan primers so that can rule out reloading. The areas where the brass is deformed by the flutes could cause areas of weaker brass. I assume that this could be corrected with annealing the whole case, but in my mind it wouldn't be worth the risk.
  6. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    I agree with the advice from RCBS. I've run across a few of these cases and the "fluting ridges" and they were just dumped in my recycle bucket. They looked like crap even after a trip through the sizing die and just looked like a split case in the making. If .308 brass was scarce I'd consider using it but there's so much out there one can be picky.
  7. elsie

    elsie Way over there on the left Well-Known Member

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    I have a HK91 which produced the fluted marks on the brass. I have also been reloading them for 20 years. I have not had any problems with them. I do use a full length die which will take some of the ridge out, but it is still clearly visible. The only case failures I have run into are neck cracks which did not cause any malfunction in the rifle. Reloaders run into neck cracks all the time with brass that has been reloaded often. If I annealed the necks of my brass, it would probably last even longer.

    I know just enough about metals to know that there is some effect on the properties of the case, most likely internal strain due to metal flow. But in my experience, it has not sufficient to cause a problem, such as full length case splits or ruptured cases.

    But as deadshot says, there's enough .308 brass out there. If you have any concerns, pass on that brass.