Inside the case neck

Discussion in 'Reloading' started by LRHWAL, Feb 7, 2009.

  1. LRHWAL

    LRHWAL Well-Known Member

    Messages:
    422
    Joined:
    Jan 11, 2006
    I'm going through a bit of a compulsive stage again (not sure I was ever out of it). Anyhow, I did a search for something else and found this thread:

    http://www.longrangehunting.com/forums/f19/how-do-you-get-low-es-velocity-number-25259/

    After reading this I'm wondering if anyone had any "eureka" moments on the topic of cleaning inside case necks recently (or in the past) that they are willing to share?

    It all got me thinking again and I have posted on this before.

    I'm still of the opinion that consistent tension is largely determined by the uniformity of the internal finish of the case neck. It seems logical too. I started seeing great ES numbers with a caliber that I load with an expander - which seems to consitently polish (burnish?) the internal surface of my ultrasonically cleaned necks. They look incredibly smooth and shiny compared with any other case necks that I've cleaned in various ways. It made me wonder about the polishing idea that many seem to warn against.

    I also tried dipping some necks in a Redding Dry lubricator (the little ceramic ball deal) which in VERY LIMITED testing worked quite well despite my concerns (and those of others I've read) that applying dry lube consistently is actually impossible as it doesn't adhere evenly to the surface of the brass. This worries me that bullet release may not be perfectly straight if pull varies around the circumference.

    I read Steve Shelp's comments in the thread I linked (pretty much what I've done in the past). And Shawn Carlock's (which I tried recently).

    Shawn, how do you clean the neck inside before dry lubing?

    I agree to some extent with with both those views! I do know that tension is not the same with ultrasonically cleaned necks and carboned necks, but getting it consistent for full diameter is becoming a pain with my brass brush approach (particularly in an ultrasonically "almost bare metal" neck as there are always little patches of carbon). I'm almost thinking not going the ultrasonic route makes consistent results easier with less effort. That, or I need to try with the case necks standing out of the liquid.

    Has anyone done some testing on ES / SD's with various approaches?

    Thanks for sharing any recent findings.
     
  2. Mikecr

    Mikecr Well-Known Member

    Messages:
    4,265
    Joined:
    Aug 10, 2003
    How do you 'know' this?
    Have you invented a tool that actually measures tension?
    If so, I'm interested. My pressure trace offers an electronic measure similar to K&M's mechanical measure -for seating force(which is not really tension).

    I don't clean inside necks anymore than the rest of the case(through vibratory cleaning), and I've achieved ES<10 as measured from an Oehler with 20' screen spacing. I get it with efficient powder burn and necks .0005 under cal(fitted necks).

    I can't imagine neck friction affecting anything really as the neck expands to release the bullet before any movement occurs. But tension matters because of the affected pressure spike and barrel timing.
    If you really want lower variance in tension you must go low with it. Less tension equals less variance in pressure needed to release the bullet.
    Tension variance in necks ~.003 under cal, creates very high ES.
    This is common, and often 'worked around' by stress relieving(misnomer annealing) the necks fairly often.
     

  3. woods

    woods Well-Known Member

    Messages:
    965
    Joined:
    Jun 4, 2006
    I have not done any tests with case necks prepped in different ways. Normally I use steel wool wrapped around a 22 caliber brush so that it is a very tight fit in the case neck
    [​IMG]

    This removes everything including all burrs and scratches. I also dip the neck down into mica afterwards and wipe it off the outside, leaving full coverage on the inside.

    This all helps get consistant seating depth for me.

    If I outside turn or inside neck ream, the inside is always all scarred up
    [​IMG]

    and the steel wool will greatly improve the inside neck surface
    [​IMG]

    It always seemed to me that the bullet would have to be moved to the lands and even partially down the bore before the expanding gases would occupy the case neck and expand the brass to the chamber neck. If that were so then varying bullet release would make a slight difference in the pressure progression. Anyway it is worth the effort to me to get 100% consistant bullet seating depth which I do know affects accuracy.
     
  4. J E Custom

    J E Custom Well-Known Member

    Messages:
    7,311
    Joined:
    Jul 29, 2004
     
  5. LRHWAL

    LRHWAL Well-Known Member

    Messages:
    422
    Joined:
    Jan 11, 2006
    Mike,

    I'm gullible so I believe what I'm told :).

    You are correct of course - I was referring to seating force and therefore I believe (right or wrong) "bullet pull". I see your view is that friction is not relevant as the bullet is not released against this friction.

    I'm not saying it's not so, but on that basis not cleaning necks at all, or bare metal and carboned up mixed up should make no difference and I'd certainly not expect that's the case. I've always had lower SD's with a consistent approach to cleaning necks. Maybe I'll try both and see where we get at some point testing on the same day.

    Just to understand the information you shared; are you speaking of tension of approx 3thou under loaded round diameter when you say under "cal" (i.e. 3 thou under cal if measuring ID and not OD). Thanks.

    Anyhow, time permitting I'll try a few appraoches here and see where it leaves me.

    I'm not unhappy with what I do and my results seem fine to me, but as I said, the compulsive bug got hold of me again.

    Thanks for all the replies.

    WL
     
  6. Mikecr

    Mikecr Well-Known Member

    Messages:
    4,265
    Joined:
    Aug 10, 2003
    .003" under cal is .003 ID -under bullet diameter

    My contention is that neck friction, if an influence to ES, amounts to nothing -compared to tension. So I'm content to leave a consistent carbon layer in the necks.
    I don't feel the need to ultrasonically clean the inside of my cases either...