What Size Mandrel?

Discussion in 'Reloading Forum (All Calibers)' started by mike06, Jun 11, 2019.

  1. mike06

    mike06 US ARMY 1970-1977 Silver $$ Contributor

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    I am thinking about buying a Expander die and mandrels from 21st century. Now that they offer custom sizes what ones do you think would be best for a 308? I do anneal and I have FL bushing dies and a neck bushing die both Redding. I believe you will always get a little springback in the case neck. What has been working for me is .0015 to .002 neck tension. I use Peterson and lapua brass
     
  2. D-4297

    D-4297

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    I use the .307 and .3075 mandrels for my Lapua brass . Also anneal every firing and use bushing die . I try to get .0005 to .001 , and use Dry Lube when inserting my bullets .
     
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  3. mike06

    mike06 US ARMY 1970-1977 Silver $$ Contributor

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    I was thinking about the same sizes .307 for sure just uncertain on the second one. I am at 30+ firings with the Peterson SRP best stuff I have ever used and when I weighed 50 of then they were all within 1.5 grains except for 2. Primer pockets are still tight.
     
  4. D-4297

    D-4297

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    Glad your having better luck with the Peterson brass . Mine , not so much . But I could have pushed them a little to hard , too . :eek:
     
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  5. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    How much are each size? I can get mine in .0001 inc for around $3 each. Porter precision products. Do a search on here and see just how nice they are
     
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  6. mike06

    mike06 US ARMY 1970-1977 Silver $$ Contributor

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    Dusty does Ken make mandrels for 3 bucks each wow I am trying to find him
     
  7. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Vermont gage makes the pins. Available from ebay or any other supplier of that type stuff
     
  8. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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  9. mikecr

    mikecr

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    With necks not completely killed by over annealing, and given a choice, I'd go .3080"
    This is basically pre-seating, in that you're using a mandrel to do beforehand what a seated bullet does anyway.
    Better to let a hardened mandrel do it.
     
  10. mike06

    mike06 US ARMY 1970-1977 Silver $$ Contributor

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  11. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    With the way the brass springs back .3080 aint gonna do much good. Not sure what size you need exactly for the firing cycle on which brass but youll need an assortment above that and a .3080 probably will not be used
     
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  12. dkhunt14

    dkhunt14

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    I like .306 for my WSM. Matt
     
  13. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    A .3060" mandrel will give you ~.0025" neck tension (interference fit). The spring-back works in the opposite direction from that of a bushing die approach, so the mandrel will generally give you somewhere around .0005" more neck tension than than simply subtracting the mandrel's diameter from the caliber. To some extent, you might be able to control this by careful selection of the bushing used to size the neck down prior to the mandrel step. For Lapua Palma brass, a 0.336" bushing [alone] gives me very close to .002" neck tension. I have also sized down necks using either a 0.335" or 0.334" bushing, then followed up with a 0.306" mandrel. The necks sized with the .334" bushing followed by the mandrel gave slightly higher neck tension than those sized first with the 0.335" bushing, suggesting slightly more spring-back. If you're after ~.0020" neck tension, a mandrel of about .3065" ought to get you pretty close and be a good place to start. However, having a set of mandrels that cover a given range would be the most useful for fine tuning neck tension as has been mentioned.
     
    Last edited: Jun 12, 2019
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  14. mikecr

    mikecr

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    The only way to get >1thou of spring back gripping force is with FL sizing of necks(including donut area), which I would never do.
    There is no such thing as 2thou tension for partially sized (no longer than seated bearing), as brass only springs back to grip ~1thou of force (max).
    So if you use a cal diameter mandrel, the brass will spring back from this, ready for bullet seating at as much force as it has to offer, times the area of grip, with no excess.
    Any sizing in excess of this, one way or the other, is wasted energy. Nothing consistent nor good in it.

    Go ahead & test it. Measure a neck, seat a bullet, pull that bullet, measure the neck. It springs back .5-1thou from cal. Tension here (grip) is that amount of potential force against an .xxx area of bullet bearing.
    You adjust tension by setting the area that normal ~1thou spring back interference is to grip. Or, you adjust the spring back force itself, through annealing to lower it, or hardening to raise it.
     
    Last edited: Jun 12, 2019
  15. mike06

    mike06 US ARMY 1970-1977 Silver $$ Contributor

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    Ordered Die and mandrels from 21st Century
     
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  16. RussellJ

    RussellJ Silver $$ Contributor

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    I purchased the system in the attached link and purchase inexpensive pin gages from McMaster Carr.
    http://forum.accurateshooter.com/threads/the-ultimate-solution-to-neck-tension.3909740/
     
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  17. David Christian

    David Christian Gold $$ Contributor

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    @mikecr, I’ve done your exact test and completely agree. I anneal my Lapua brass after each firing and only get 0.0005 spring-back in my brass. Therefore, in my .284 I use a 0.2840 gage pin just before bullet seating.
     
  18. mikecr

    mikecr

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    So in David's plan he could squeeze necks down 0.0015 under cal. They would spring back outward from the bushing 0.0005 leaving 0.001 under cal(actual sized). Keep in mind that this is not usually what is stamped on a bushing..
    Then he could expand with his 0.2840 pin, and the necks would spring back inward to 0.0005 interference for bullet seating. It's one part of minimal sizing, if setting sizing LENGTH to no more than seated bullet bearing. And he could adjust his neck tension to roughly half, by reducing that sizing length by half. Another part of minimal sizing is not letting necks expand much during firing, via tight neck clearance.
    And it's very important that any plan employed here is established before & during load development.
     
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  19. D-4297

    D-4297

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    I'm doing almost exactly what Ned Ludd recommended in his post . The difference being , that I'm using the .335 bushing , followed by the .3075 mandrel , ending up with a .307 I.D. on my Lapua Palma cases for my F-TR , .308 cases . I use the same set-up for my 7.62 x 54r Win cases , with a Whidden custom bushing die , and get a .3075 I.D. Little softer brass on the Win cases , but they have eight reloads on a "F"-Open load . I think the goal is to arrive at the inside case diameter that you are after , no matter which method is used .
     
  20. glider

    glider Gold $$ Contributor

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    which dry lube and how do you apply . dip bullet base ?
     

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