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Case neck tension - what a difference

Discussion in 'Reloading' started by PCJim, Aug 19, 2012.


  1. PCJim

    PCJim
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    I decided to finish loading up some 308 precision rounds this weekend that I had begun working on several weeks ago. 80 cases were Federal that were previously fired in my SPS that were neck sized only; 15 cases were RPU that were FL sized that I wanted to run as an experiment (how much of a group difference would they make as compared to the cases previously fired thru the SPS).

    What I found while loading the 168gr SMKs was that there was a very noticable difference in the neck tension between the FL and neck-only sized cases. The neck sized cases (Lee collet die) had just barely enough tension to hold the bullets - adequate, but not nearly as tight as the FL sized cases (RCBS).

    This should add some additional insight on how these neck sized rounds shoot. The cases previously fired in the SPS were new Federal brass that was initially prepped by FL sizing during the loading. They were able to give me a five shot .583 grouping (100yds) during load development.

    :shocked: I know Steve is going to jump in here and offer up that I should have taken multiple ID and OD measurements. I now think that doing so could have been rather informative. Maybe I'll go out and take some readings on other once-shot brass later on tonight.

    Has anyone else noticed any differences in neck tension between neck sizing dies and FL dies?
     

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  2. Colorado4Wheel

    Colorado4Wheel
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    Just to be accurate it's I.D. that you want as well.
     
  3. steve4102

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    Lee sets up the Mandrel size for approximately .001 neck tension. I polish my mandrels down to increase neck tension on all my Collet dies. You can also order a Reduced mandrel directly from Lee.
     
  4. Hoser

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    Neck tension is tricky. For single shot rifles .002-3 is plenty. Mag fed rifles need a little more.

    However what matters is downrange results and a low ES and SD across the chrono. Sometimes more neck tension will bring down the ES/SD.

    At short to mid range it isnt a big deal. Past 600 yards, big deal.
     
  5. fredj338

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    ^^THIS^^ I Only have one set of the Lee neck dies, but found the neck tension not to my liking so ploished the mandrel down.
     
  6. PCJim

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    If the wind lays down enough this upcomming weekend to shoot these rounds, I'll post the results. If the neck sized brass doesn't deliver similar results to those obtained during load development, I'll consider polishing the mandrel down a bit.
     
  7. squirreld

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    How do you polish down a carbide button expander ball?
     
  8. steve4102

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    Duno. The Lee Collet die is nether carbide or an expander ball. It is a steel mandrel that can be reduced or polished down by chucking it into a drill and polished with fine emery cloth.
     
  9. WiskyT

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    Lee collet die: I am not a "rifleman". I haven't loaded much more than a few hundred 30-06 rounds and they all have been with the Lee collet die. When I started out, I was using a Lee hand press. I had some rounds with very low neck tension. I didn't measure it with instruments, but it was obvious that there wasn't enough tension as some bullets slid into the cases.

    Since I switched to using the same dies, same brass, same bullets, and same rifle, with my RCBS Junior press, I no longer get any neck tension issues. The reason is I'm able to apply much more pressure on the collet. The Lee instructions understate the ammount of pressure needed to size the neck properly. You really need to bare down on the thing to make it work. Adjust the die body down a bit further so you really cam over on the linkage and it should work fine.

    Dressing the mandrel down might work as well or better, I haven't tried it. First I would try adjusting the die body down and see how it works as I always try the easy solutions, especially ones that don't alter equipment, first.
     
  10. fredj338

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    You would need special diamond grinding setup. As noted, doesn't matter as the Lee is just steel.
    Adjusting the die down may work, but go too far & you crush cases. Don't ask how I know.
     
    #11 fredj338, Aug 21, 2012
    Last edited: Aug 21, 2012
  11. WiskyT

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    You crushed a case with a Lee collet die?
     
  12. Boxerglocker

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    I need to experiment with my Lee 223 collet die. I ordered some Lapua brass, after I form fire it I will neck size only.
    I also heard that moving the die too far down will crush the shoulder. So Fred polishing the mandrel down... how much, 0.002?
     
  13. fredj338

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    Oh yeah, easy to do. Just screw the die in too far.:wow: The whole case doesn't crush but the neck/shoulder does.
    Polsihing down as little as 0.0005" is enough for most brass, 0.002" is actually quite a lot.
     
    #14 fredj338, Aug 22, 2012
    Last edited: Aug 22, 2012
  14. WiskyT

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    I'll have to keep on my toes regarding that.

    As for how much tension, I'll leave that to you and Hozer etc, guys who have tired different levels of tension and seen the results. According to Lee, any more than 0.001" is wasted because the brass stretches anway. His instructions are geared to "normal" reloading though, and not precision shooting.

    Maybe I will polish my mandrel down a lrch next time I use it. It sounds easier than bearing down on my press and hoping something doesn't pop or a shoulder collapse.
     
  15. Boxerglocker

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    This guy had some good insights. I took his suggestion of polishing down the collet bevel to smooth it out and using a touch of lithium grease. I polished the mandrel down another 0.0005 and give it a once over with flitz.
    Experimented a little with some brass and got it adjusted to my liking. I'll have to check measurements when I get my Lapua brass.

    [ame]http://youtu.be/mhTUgytUGnM[/ame]
     
  16. Colorado4Wheel

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    If you read that link I posted a couple post back you will see others have found brass spring back to be in the .002-.003 " range. Lee seems to think brass has very little spring back. Others seem to think it has more. My measurements show it to be WAY more then .001" (which is not a lot). To me it's pretty obvious that brass sized .001" under the bullet size has way less neck tension then a case sized .002" under bullet size. Others in this thread seem to agree.

    Basically, Lee is wrong on this and he drives me nuts.. :rofl:

    I just had to say it.

    Carry on. :wavey:
     
  17. Hoser

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    Best fix is to just get Redding or Forster bushing dies and go to work.

    The whole polishing down a mandrel thing to get the right size seems like a lot more work than it needs to be.
     
  18. WiskyT

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    Uh, that' not what Lee is saying. He's not talking about spring back. He's talking about no matter how small you make the ID, it will stretch with the insertion of the bullet so that it is no more effective than if it had been 0.001" undersized to begin with.

    He's not saying if you squeeze it to 0.305" it will bounce back to 0.306", what he's saying is if you size it to 0.305", or 0.307", it will not grip the bullet any more firmly.
     
  19. WiskyT

    WiskyT
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    It depends on what you want to do. For $20.00, I have a die that makes ammo with a load that I picked out of a Hornady manual that shoots 0.75MOA out of a $250.00 Stevens I bought on clearance at Dick's.

    My die works fine as is. It worked well overall with an occasional glitch until I learned how to use it properly. I'm fence sitting as to whether I want to spin the mandrel in a drill and polish it with a Scotchpad.

    Some Palma match guy or whatever (1000 yard) held the world's record for a few years using the Lee collet die. If it's good enough for him, it's good enough for me.
     
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