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What is a proper crimp?

Discussion in 'Shooting Related Threads' started by grntitan, Jun 26, 2011.

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  1. grntitan

    grntitan Well-Known Member

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    I read on various threads from time to time about good crimps, dished crimps, bad crimps etc. etc. What exactly is a good crimp? What is a dished crimp? What would be a bad crimp? Here are some pics of mine. Are these good crimps? Can someone school me on how to ID good crimps?



    grntitan_2009_250328.jpg


    grntitan_2009_250330.jpg
     
  2. Unknown1

    Unknown1 Well-Known Member

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    Yours look very serviceable: I don't think minor dishing is an issue.

    My main concern is that the crimp is proper depth (.055"-.060" deep, thickness of a dime) because the crimp depth effects the chamber pressure can also effect the shot velocity the load produces. Swirls or little center holes have no bearing on the pressure produced by the crimp shoulders.

    Otherwise, as long as everything stays inside and the petals aren't bulging up, to me it's a good crimp.

    MK
     
  3. grntitan

    grntitan Well-Known Member

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    MK--So my crimps although usable, are dished? I say this because the factory loaded shells i have look almost identical to these. That is ultimately how i set my machines. That is to look like factory shells. Maybe i shouldn't do that?? What is the drawback of too much dish?

    I also notice the more roll top i add the more it dishes. With these reloads i have backed way off on the roll finish die.
     
  4. GrandpasArms

    GrandpasArms Active Member

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    I accept any crimp where the shot stay in the hull.
    I can't tell the difference.

    Larry
     
  5. whiz white

    whiz white Strong Supporter of Trapshooting Banned

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    If there were loaded on a P/W, I would LOWER my pre-crimper about 1/16-1/8". That should take care of the new style AA hull too.

    The STS & Nitro's look fine.

    Whiz
     
  6. Unknown1

    Unknown1 Well-Known Member

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    <blockquote>"MK--So my crimps although usable, are dished?"</blockquote>No, your crimps look darn good; I was simply stating that IF a crimp had a slight dish to it it didn't see that as a fault. From the photos, yours are not dished.

    I've never had loads tested with excessive dishing for pressure and velocity. I've been meaning to send some off to see what they do. I'm guessing that the peak pressure would be low and the velocity of the shot will suffer, but I don't know for sure.

    MK
     
  7. Dave P

    Dave P TS Supporters TS Supporters

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    I think too much is made of perfect crimps. Sure they look pretty and it's what you expect of factory shells. A little hole or a little bulge never mattered to me. It's just not that big a deal.
     
  8. craby boy

    craby boy TS Member

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    There is a very good article in clayshooting USA showing several depth of crimps and their pressure and velocity,if you goggle crimps the magazine and Tom Ceretto , you should find it.Above advise is correct .050 is good.

    Craby
     
  9. Rastoff

    Rastoff Active Member

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    A good crimp is one where the shot doesn't fall out.
     
  10. Shooting Jack

    Shooting Jack Active Member

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    My book tells me that the pink one is not good and I believe it says to raise the crimp starter. The only thing I am talking about is the twist to the crimp petals. However, if I could load all those variations without reseting then I could accept the twist. Then again, someone can say I'm wrong. LOL Jackie B.
     
  11. grntitan

    grntitan Well-Known Member

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    " if I could load all those variations without reseting then I could accept the twist"

    Exactly. I could adjust all the crimp dies and probably correct it but i load 100 to 1 or more Remington STS hulls to all other hulls. I leave the machine set for them. All others i take i what i get. That other amounts to maybe a few 100/year. For what its worth, some of the Pink Federals turned out with no twist at all. The one i grabbed for the pic was obviously not one of them.
     
  12. JerryP

    JerryP Active Member

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    I adjust the loader using a Win hull to duplicate the factory crimp. Do not adjust using a Rem hull because they are generally longer. Rem and Fed will then load fine.
     
  13. SBray

    SBray Active Member

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    Craby,

    Is this the article?

    http://www.clayshootingusa.com/html/archive/aug_sep10/Cases%20and%20Crimps.pdf

    Steve
     
  14. Unsingle

    Unsingle Member

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    grntitan - I wouldn't change a thing. Just stay consistent on your crimps. Once my loader is set up properly, I never change a thing.
     
  15. grntitan

    grntitan Well-Known Member

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    "Do not adjust using a Rem hull because they are generally longer"

    Jerry-- Thats ok if your not loading Remington hulls. If all you load is Remington hulls(like me) then thats what you should use to adjust your dies. Now if all i loaded was AA's, i set it for them.
     
  16. JACK

    JACK Well-Known Member Supporting Vendor

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    I've seen that Cerrato article before. The far right hand shell/crimp looks factory. MIne lok like that. Pressure is not the enemy of autos that he says is so devastaating. Adn who wears out a gun anyway? Yet to see one worn out. Abused? Neglected? yes.

    I'm with "unsingle" 100%. Get it set up and load away.
     
  17. late bloomer

    late bloomer TS Member

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    Neiln Winston posted several years ago his very detailed personal research on crimps and their impact on patterns etc. He found it didn't make much difference.
     
  18. psfive

    psfive Member

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    A good crimp is one that holds the shot in. The ones in the pic above look good to me. They look just look mine. Paul in Nebraska.
     
  19. Unknown1

    Unknown1 Well-Known Member

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    <blockquote>"I've seen that Cerrato article before. The far right hand shell/crimp looks factory. MIne lok like that.</blockquote>According to the caption of the picture... the shell in the center is the one loaded to SAAMI specs (about .060").<br><center>
    [​IMG]

    <br>
    The two on the right are over-depth and will be over-pressure.</center>

    MK
     
  20. Recoil Sissy

    Recoil Sissy Well-Known Member

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    The photos added by Unknown1 are worth a close look. None of them will leak shot but ballistics and performance will vary significantly.

    There's a strong correlation between crimp depth and chamber pressure. In one study various crimp depths like those shown above were pressure tested. Excessive crimp depths (like the shell on the far right) jacked pressures up by 2000 psi. That's enough to push a recipe on the upper end of acceptable to overpressured.
     
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