Neck turning and Blown primers

Discussion in 'Reloading' started by Lyons7STW, May 2, 2014.

  1. Lyons7STW

    Lyons7STW Well-Known Member

    Messages:
    219
    Joined:
    Sep 7, 2011
    So I have a .260 rem. I've been shooting Precision matches with.
    My load was a 140 Berger over 41.4 grains of H4350 with a COL of 2.850
    I was having some chamber a little tight and decided to turn the necks. Took of a thou.
    Not even 100% clean up on the neck.
    Loaded some up using same old formula. Blew 3 out of 4 primers.

    Was not expecting that!

    BTW. Book on that load is 41.2 in berger manual
    @ 2.830
     
  2. Lyons7STW

    Lyons7STW Well-Known Member

    Messages:
    219
    Joined:
    Sep 7, 2011
    Guess I should state that I had worked up to the load prior to turning.. And a little past it, but it shot best. It had over 100 rounds through it with no issues.
    I also double checked my scales and they are still spot on. So that wasn't the issue.

    Just a little shocked that shaving a hair off the neck caused such a pressure jump.
     

  3. Mikecr

    Mikecr Well-Known Member

    Messages:
    4,263
    Joined:
    Aug 10, 2003
    Turned necks do not cause higher pressures.
    Be sure your headspace is not excessive and that your trim length allows clearance from chamber end (headspace included).
     
  4. BountyHunter

    BountyHunter Writers Guild

    Messages:
    4,803
    Joined:
    Jun 13, 2007
    Your problem IS NOT turned necks!

    1. Excess headspace? is it hard chambering?

    2. Changed lots of powder?

    3. Are you NS only? If so, forget it and get a body die or FL die and learn how to set it up to just push the shoulder back no more than .002
     
  5. Reloader222

    Reloader222 Well-Known Member

    Messages:
    208
    Joined:
    Jun 4, 2010
    Check for donuts on the inside of the case where the shoulder meets the neck. After firing a case, insert a bullet in the neck. If it get stuck you have a donut and will have to cut it out with a reamer (Foster). Then it cauld also be that the cases had harderned - do you anneal them after 4 reloads or so?

    Then check the diametre of the primers you are using compared to the one's you used before. I use a very old batch of Winchesters LR and Magtec LR since they are a few thousands larger in diametre and therefour would give you a proper seal. It could also be that the primer pocket had stretched after several firings. Then you need to adjust the primer to those cases.
     
  6. EddieHarren

    EddieHarren Well-Known Member

    Messages:
    1,046
    Joined:
    Nov 27, 2005
    Check your case length as well.
     
  7. Lyons7STW

    Lyons7STW Well-Known Member

    Messages:
    219
    Joined:
    Sep 7, 2011
    Trim length has not changed. Head space has not been an issue for the last 379 rounds down the tube and nothing about my case prep changed other than the OD neck turning and ID reaming.
    These cases are once fired Fed. Gold medal match that I FL resized. ( I know They are not the most desire able cases but I have a healthy supply issued to me). I have probably spent more time and tooling money on these cases than if I had bought Rem. Or Win.
    I did have to pop open a new case of primers and another can of powder at this juncture. I'm running Win. LR primers.


    I have never seen enough fluctuation between Lots before for that to have been my first conclusion. But that is where I will look now.
     
  8. EddieHarren

    EddieHarren Well-Known Member

    Messages:
    1,046
    Joined:
    Nov 27, 2005
    I was not referring to headspace but OA case length. Often times when pulling the expander ball back through the case neck, they stretch.
     
  9. Lyons7STW

    Lyons7STW Well-Known Member

    Messages:
    219
    Joined:
    Sep 7, 2011
    Over all case length is .005 under book trim length and within .001 over the entir batch.
     
  10. phorwath

    phorwath Well-Known Member

    Messages:
    4,896
    Joined:
    Apr 4, 2005
    Based on everything you said you've already checked, and if you've heeded the possible culprits already identified in this Thread - the likely possibility is that your powder is now creating increased pressure. It's not unheard of for a new Lot of the same Brand of powder to yield higher or lower pressure than a previous lot. Also need to double and triple check you powder scale (balance beam or digital) is calibrated correctly.

    If they're still chambering tight, you ought to make absolutely sure your case necks aren't being pinched/wedged along the neck of the case, where the chamber might be trying to swage the neck w/seated bullet into too narrow of a chamber neck diameter. This comes back to the possibility of a donut formed inside the case neck, the case necks being too long, a batch of overdiameter bullets, or anything else that could cause the outside diameter of the loaded cartridge case neck to be too large in diameter to fit into the chamber neck.

    Measure the OD of the neck of some of your loaded cases and see if there's any measureable difference. You said you've fired these cases a number of times. The thickness of the case neck will typically increase at the case shoulder/case neck with repeated firings.

    Last thing I've read about, but never experienced since I don't shoot enough between cleanings to experience it, is to make sure a carbon ring isn't forming in the bore just ahead of the case neck.

    But you said you just changed to a new can/Lot of powder, so I think you're overlooking the most obvious potential culprit - unless your casings still chamber with difficulty.

    Let us know what your finally conclusions are? Always look forward to learning from others' experiences.

    PS: Believe it or not, I just measured some 7mm bullets that measure 0.282" in outer diameter. They slid into my prepped case necks too easily so I began measuring things.
     
  11. Lyons7STW

    Lyons7STW Well-Known Member

    Messages:
    219
    Joined:
    Sep 7, 2011
    As for the donut. One is not discern able and the ID reamer in the neck turning operation is supposed to elevate one if present. It did not appear to be cutting any material. The dropping a bullet into the fired case method is a no go. If a fella desired he could have taken these fired cases, reprimed, recharged them and loaded them. The neck was tight enough that post firing/ post spring back it was just as tight as initial bullet seating. Hence the neck turning. Post neck turning and firing bullet bearing surface will still not enter neck of case without pressing it.
     
  12. Lyons7STW

    Lyons7STW Well-Known Member

    Messages:
    219
    Joined:
    Sep 7, 2011
    I have measured every dimension I could think of on fired cases, loaded cases and cases prepped to be loaded. I have no method to measure variances in powder but the one thing I have found is post bullet seating a slight increase (0-2 thousandths) in diameter on some of the cases at the case body/ shoulder junction. This brings my seating die setting into question. In my opinion. I did not consciously change it. And don't recall it being loose at any point but a lot has occurred since now and originally setting it. Could it be possible I was getting some unintentional crimp along with a little crush on the case in the seating operation and causing some pressure?


    It will be a bit before I can fire some rounds and have solid conclusions.
    I do want to mention I appreciate y'all's help and insight. It really helps. There is A LOT going on in this quest for 1000 yard accuracy .
     
  13. Kennibear

    Kennibear Well-Known Member

    Messages:
    492
    Joined:
    Jul 24, 2012
    Considering all the work investigating the chamber/ case fit you've done my suspicion is that new can of powder. I once bought 4 cans of WW 680BR from a store that was closing in CA and then moved to Idaho. Didn't open the cans for about 5 years but when I did I found they contained a mix of powders, one of them being something with color dyed flakes in it. WW 680BR is a Ball Powder! That was four cans of fertilizer!

    Check the powder. Twice. You pretty much ruled out the other stuff.

    KB
     
  14. Bullet bumper

    Bullet bumper Well-Known Member

    Messages:
    1,040
    Joined:
    May 20, 2009
    You changed powder lot and primer lot and you are loaded at high pressures to start with. So that is always a risk to get a change in acceptable pressure levels. You were just unlucky that the new powder lot is faster and the new primers softer and the temp on the day may have been higher than usual .
    Staying down in pressure closer to reccomended levels tends to take account of many of these kind of lot variations .
    Neck turning for a factory chamber in this instance can't raise pressures . I have never seen that happen .