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Thread: How to choose the right expander plug for cast in military rifles

  1. #1
    Boolit Man Kegcaissy's Avatar
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    How to choose the right expander plug for cast in military rifles

    Hi!

    I'm looking to get some info about the rcbs and noe expander unit. As far as i know, the rule to use these is the bullet diameter minus 0.003"-0.004" to get some tension on the boolit. While looking for customs expanders because rcbs does not have what i need in size, i read on the noe website that they recommend using their expander plug 0.001" larger thanthe bullet.

    What would you do? I intend to shoot 0.316"-0.317" boolits. Do i need a custom 0.314" rcbs style expander or follow what noe recommend and get a 0.317" expander plug (i already have the lee die for it)? Am i missing something here?
    Last edited by Kegcaissy; 01-07-2019 at 06:30 AM.
    We really need a Ar-15 subforum!

  2. #2
    Boolit Master

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    The NOE expander plug , that fit in the lee flaring die expands in 2 steps like a Lyman m die . The top steep is slightly larger to make starting your boolits smoother , while the lower section expand smaller to still hold neck tension .

  3. #3
    Boolit Master
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    I don't think there is a clear hard and fast rule as the hardness of the alloy and powder being used all come into it. I myself do not like to have the cast held that firmly as they are distorted. My 375 Whelen likes cast at .378 so my expander is .376, any tighter and accuracy suffers. My 357 Maximum rifle likes cast at .360 given the barrel is .358, so I am going with what Noe suggest and use an expander .0001 over that diameter and this should give me a perfect hold on the cast after the brass spring back. I believe that we tend to crimp our cast too tightly in many cases to the detriment of accuracy. I realise these rifles of mine are not military but the principal is the same from my observations. All this works for me but I would be interested to see if it works for you as well. Regards Stephen

  4. #4
    Boolit Master

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    I see NOE has step expander plugs in .316 x.312 and .318 x.314 , I have no experience with the RCBS expander die .

  5. #5
    Boolit Grand Master


    Larry Gibson's Avatar
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    There is always going to be a certain amount of springback with the expanded neck. Noe lists, as mentioned, 2 diameters for their expanders. Get the NOE expander with the large diameter .001 over the bullet diameter.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  6. #6
    Boolit Man Kegcaissy's Avatar
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    What i understand of the noe expander is that the first number is the flare size and the second number is the expanding size. I'm going to try the 318x314 to get 0.003" of neck tension. But, before that i want to hear how others are doing this.
    We really need a Ar-15 subforum!

  7. #7
    Boolit Man Kegcaissy's Avatar
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    Quote Originally Posted by Larry Gibson View Post
    There is always going to be a certain amount of springback with the expanded neck. Noe lists, as mentioned, 2 diameters for their expanders. Get the NOE expander with the large diameter .001 over the bullet diameter.

    In that regard i will need a 322x318 to shoot 317" boolits.

    Thank you sir!
    We really need a Ar-15 subforum!

  8. #8
    Boolit Grand Master


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    No, you should get a .318x.315 for a .317 bullet.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  9. #9
    Boolit Buddy
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    I have about 20 of the NOE expanders and i almost always split the two numbers down the middle.

    eg. for .358 bullets i use the .360 x .356 expander.

    I find this gives me .002 of neck tension and a .002 bell that most sized bullets will sit into nice and square ready for seating.
    If i have difficulty seating or notice any shaving i go up .001 to the next size.

  10. #10
    Boolit Master
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    I use the RCBS system and routinely use an expander .001" smaller than bullet diameter with just the faintest bit of flair to ease the bullet into the neck. I keep my case necks annealed, so I doubt I'm getting much if any spring back. Bullets easily pass the old CBA "shake the bugger like a fresh new bottle of ketchup" test for tightness/definition of "fixed ammo" rule, and never an issue when hunting with them either. Of course, I'm sizing my bullets to .0005" (half thou) under throat diameter too, or strive to anyway.

  11. #11
    Boolit Master Tenbender's Avatar
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    NOE is the way to go.

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BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
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