New 155gr 6.5mm Berger on the horizon?

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by Grimstod, Aug 18, 2017.

  1. Shane Roya

    Shane Roya

    Joined:
    Jan 12, 2017
    Messages:
    35
    QL shows .264, 155, Sierra HPBT LR MatchK 9570, apparently Sierra does not make it anymore.
    http://forum.accurateshooter.com/threads/sectional-density-and-long-range-bullets.3738166/
    see second post down
     
  2. Grimstod

    Grimstod

    Joined:
    Jan 23, 2014
    Messages:
    1,316
    Use a drop tibe. I have a short freebore (.167) and can get in 42 before i hit compression
     
  3. fredo

    fredo Silver $$ Contributor

    Joined:
    Feb 6, 2015
    Messages:
    737
    If I were you, I'd remain skeptical about the associated pressure penalty likely to be encountered.
    There's no "free lunch" in Physics...
     
  4. Grimstod

    Grimstod

    Joined:
    Jan 23, 2014
    Messages:
    1,316
    Do you season your brass before starting load development?
     
  5. fredo

    fredo Silver $$ Contributor

    Joined:
    Feb 6, 2015
    Messages:
    737
    Define "season"

    If you're inferring about firing new brass in the chamber before actual testing, then...yes.
    Easy to do when you're FF-ing for a wildcat, or any necked up/down cartridge. Makes good sense to let the brass form to that particular chamber, then minimally resize them before stomping on the pedal during pressure testing...
     
    Last edited: Sep 13, 2017
  6. Grimstod

    Grimstod

    Joined:
    Jan 23, 2014
    Messages:
    1,316
    I may be using the wrong term "Season". To me its brass that has had a mid range load run through it for at least three reloads. At that point the heads of the brass get harder and I have seen, for example, my 6.5x47 was able to then handle 1.5gr of additional powder compared to when it was just fire formed once. The BRX could take another 1gr after four firings and PPC can usually handle between 1-2gr more. This has nothing to do with size of the brass, just the heads of the brass getting harder. Fire formed brass is what I would call that term and is something else to me altogether.
     
  7. fredo

    fredo Silver $$ Contributor

    Joined:
    Feb 6, 2015
    Messages:
    737
    Sorta, pretty much what I described above.
    The extra 'handling ability' could be attributed to 'hardening' of the brass from successive firings. But beyond that, a mild initial load allows the brass to 'stretch' to fit that chamber without over-pressuring/over-stressing the web area...

    If ya go too hot on any initial firing of new brass, you're most assuredly negatively affecting future case life. Not to mention, blowing out the primer pockets prematurely. Both of those instances would not help in how that case handles pressure on subsequent firings...

    My point above was about assuming the use of the same powder charge (42gr H4350) for a ~10-15% heavier bullet. A cursory glance to compare bearing surfaces doesn't account for that extra mass.
    Physics tells us that the same energy (work) against a larger mass (action) has an equal & opposite (reaction). That 'reaction' will manifest in increased case pressure...

    Just sayin', ya can't assume the charge weight for a 130-140gr bullet will be safe with a 155, based on bearing surface, alone.
     
    Grimstod likes this.
  8. 284winner

    284winner Silver $$ Contributor

    Joined:
    Dec 6, 2015
    Messages:
    1,445
    Yep I'm aware of that bullet they made some years ago. Just haven't seen it in their lineup in some time. If I'm not mistaken that 155 SMK was inferior in ballistic coefficient to the 142 SMK. Could be wrong it's been a while since I've used them.
     
    dkhunt14 likes this.
  9. JBT

    JBT Gold $$ Contributor

    Joined:
    Jan 24, 2017
    Messages:
    255
    I believe it was inferior to the 142
     
  10. 284winner

    284winner Silver $$ Contributor

    Joined:
    Dec 6, 2015
    Messages:
    1,445
    Yep was thinking that too. Probably why it was discontinued as a match bullet. No real advantage.
     
  11. ImBIllT

    ImBIllT

    Joined:
    Jun 1, 2008
    Messages:
    127
    I wonder if they would be stabile in an 8.5" twist at 3500' on a warm day...
     
  12. Grimstod

    Grimstod

    Joined:
    Jan 23, 2014
    Messages:
    1,316
    Your SG would be 1.48 so that is stable but you will loose a little BC.
     
    Last edited: Sep 22, 2017 at 7:20 PM
  13. Grimstod

    Grimstod

    Joined:
    Jan 23, 2014
    Messages:
    1,316
    More news on these bullets soon from a trusted source.
     

Share This Page