Cast bullets create higher pressure?

Discussion in 'Ammunition & Reloading' started by dgang, Jan 18, 2020.

  1. dgang

    dgang Member

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    Just perusing 2005 Alliant Reloading Guide for .357 Mag. cast bullets and found some data I don't understand.(not an uncommon state) They give 7.8 gr. of Unique for 158 gr. JSP @ 1280 FPS, developing 33,200 PSI. The same data states 6.8 gr. of Unique for a 158 gr. cast LSWC @ 1295 FPS but with a higher pressure of 33,900 PSI. I can understand the difference in the amount of powder and velocities, but fail to understand why the cast bullet with less powder has higher pressure. Any help out there?
    Thanks in advance and good shooting' to ya.
     
  2. austin92

    austin92 Well-Known Member

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    Also reload and curious. I though lead data was backed down to avoid gas checks and leading the barrel.
     
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  3. Shopfox

    Shopfox Well-Known Member Supporter

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    Does the book have the same COAL for both?
     
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  4. dgang

    dgang Member

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    Talking to others it appears that lead bullets will quickly obturate, quicker than jacketed bullets, and raise the pressure in the barrel by sealing off the gas and leading to higher pressures. Thanks for your thoughts.
     
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  5. Wambli

    Wambli Well-Known Member

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    Contrary to many myths and bad internet info, lead bullets are tougher to push down a barrel than jacketed ones.
     
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  6. Wambli

    Wambli Well-Known Member

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    Soft pure lead is. Hard cast, depending on metal alloy, properly hardened will leave many a barrel without even showing rifling marks on the bullet.
     
    Last edited: Jan 19, 2020
  7. dgang

    dgang Member

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    Just did a test of my own using a 1/4" dowel and 158 gr. hard cast SWC and a 158 gr. XTP in a 2" snubby barrel and the cast bullet was definitely easier to push through. Just sayin'.
     
  8. Wambli

    Wambli Well-Known Member

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    Great, how did you manage to generate gunpowder type pressures with a dowel?!?!? That’s cool!
     
  9. Wambli

    Wambli Well-Known Member

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    Plug your barrel with a little mud and you can clear it up with a stick. Do the same and let go of a round of ammunition and it’ll self destruct.
     
  10. dgang

    dgang Member

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    Yah, you do have a point. Can't think of any way to test that theory other then to light a couple off with little powder. Not about to do that. LOL
     
  11. PaBushMan

    PaBushMan Well-Known Member

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    I load coated hard cast lead. BHN 16-18 And have ran them at cast data and fmj data. No signs of over pressures. But always please work up.
     
  12. dgang

    dgang Member

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    Still a little confused: ( Quote taken from another forum) Speer advises not to use 158 gr. jacketed bullets in a .38, bullet may not clear barrel. Seems to contradict what is being said. Maybe the difference between lower pressure of the .38 not effecting the bullet and the higher pressure of a .357 deforming the bullet?
     
    Last edited: Jan 19, 2020
  13. PaBushMan

    PaBushMan Well-Known Member

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    Suggestion, buy some reloading manuals. I have a library of them. Never trust data given on a forum. That is why i did not list any data. I run 158 grain jacketed in my wheel guns. I have 3 one has a 4 inch barrel 2 6.5 inch ones. The bullets clear fine. 2 good manuals to start with are lees newest and lyman's newest. Also lyman's cast edition is good to have. It has loads the other does not have.
     
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  14. freefall

    freefall Well-Known Member

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    Obviously, everything I know is wrong.
     
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  15. Rifling82

    Rifling82 Well-Known Member Supporter

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    What’s it have for OAL?
     
  16. SGWGunsmith

    SGWGunsmith Well-Known Member Supporter

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    \

    Yup! You nailed it. I've shot 158 grain hard cast Lyman bullets with and without gas checks in my Ruger Blackhawk .357 Magnum, and the bare lead base will lead the bore, unless the powder charge was indeed reduced.
     
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  17. SGWGunsmith

    SGWGunsmith Well-Known Member Supporter

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    Well, the experts do say that "admission is the first step toward recovery." :p
     
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  18. SGWGunsmith

    SGWGunsmith Well-Known Member Supporter

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    I guess I missed that memo. I've shot 158 and 160 grain jacketed bullets loaded in .38 Special cases for quite some time. Haven't had a bullet get stuck yet in my S&W Model 19 4-inch.
     
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  19. Oldoutlaw

    Oldoutlaw Well-Known Member Supporter

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    Yup
     
  20. freefall

    freefall Well-Known Member

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    OK big-brains. Explain how lead bullets generate more pressure than jacketed.