Terminal performance and Meplat trimming?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by bigngreen, Nov 20, 2009.

  1. bigngreen

    bigngreen Well-Known Member

    Messages:
    5,839
    Joined:
    Nov 24, 2008
    So Bud Martins thread on the 6.5 SMK got me to wondering about what would happen with terminal performance if we would trim the meplat.
    I have seen where trimming will help your accuracy to some degree which is good but you have also blunted the point of the bullet which I would think would help some bullets like the SMK or Berger get started expanding. Or would meplat trimming be insignificant to terminal performance??
     
  2. MontanaRifleman

    MontanaRifleman Well-Known Member

    Messages:
    6,068
    Joined:
    May 21, 2008
    Making a larger HP meplat would definitely fascilitate expanding. The question is how much do you trim. Unless you have a very precise way of doing it, it would also introduce a lot of inconsistancy in external ballistics and your BC will drop.

    GS bullets have a larger HP meplat for this very reason. Terminal performance seems to be their highest prority for "hunting" bullets. They design their bullets for reliable expansin down to 1500-1600 fps, depending on the bullet.
     

  3. bigngreen

    bigngreen Well-Known Member

    Messages:
    5,839
    Joined:
    Nov 24, 2008
    I think the trimmers would set the bullet the same, I may take some Bergers and try it and shoot some wet paper out at 1000yrd and see what difference it make. I can turn a tool out on a lathe.
    This may be a moot point though, I see that there is a slight lose of BC so it's may be counter productive to try to make up for a slow bullet by slowing it down more, unless there is a marked terminal effect increase.
    I have looked at the GS bullets but I shoot .277 cal stuff and it looked like they only have up to 130gr bullets with a .410 BC, which doesn't tempt me enough. If I shot some 30 cal stuff that 177hv looks like it would be the ticket. I'm awaiting the 169.5 Wildcat for my .277 stuff.
     
  4. elkaholic

    elkaholic Well-Known Member

    Messages:
    5,346
    Joined:
    Dec 4, 2008
    Trimming the meplat will increase expansion and lower B.C. to some degree depending on how far you go. Sometimes you can drill out the tip slightly leaving the same dia. meplat but THINNING the nose section of the jacket. This can create a change in airflow with the slightly hollow pointed tip which may or may not be a big deal, but it will help expansion at lower velocity. Everything is a trade off! Test it on the range and see.....Rich
     
  5. bigngreen

    bigngreen Well-Known Member

    Messages:
    5,839
    Joined:
    Nov 24, 2008
    elkaholic
    I'll just give it a try and see what goes. I'm sure your getting bullet requests like crazy but anything 160+gr .277 would be nice :D
     
  6. Michael Eichele

    Michael Eichele Well-Known Member

    Messages:
    3,829
    Joined:
    Jan 6, 2003
    I tried this a couple of years ago. I never tested it on game due to the fact that the BC dropped off hard. I used the 190 SMK which I was running at 560+ and dropped (I cant remember exactly) but it was around .470? The 190 BTSP is higher than that so I opted not to use it in the first place after field testing it.
     
  7. bigngreen

    bigngreen Well-Known Member

    Messages:
    5,839
    Joined:
    Nov 24, 2008
    I wonder if re-pointing them would give you back you BC but create a frangible tip that would blow out and leave a large cavity to get it open faster.
     
  8. elkaholic

    elkaholic Well-Known Member

    Messages:
    5,346
    Joined:
    Dec 4, 2008
    Bign' I have had a lot of requests but I only make .308 currently. I plan on getting a few more out to various states and see how people respond. I get a REAL kick out of all the heated discussions and various opinions on long range hunting bullets. I'm convinced that the reason for it is, ALL of us are trying to do the best we can with a variety of bullets, NONE of which are designed solely for long range hunting. As I posted the other day, there are long range bullets and there are hunting bullets, but there are no "long range hunting bullets!.....Rich
     
  9. bigngreen

    bigngreen Well-Known Member

    Messages:
    5,839
    Joined:
    Nov 24, 2008
    Long range hunters are kinda a tough group to satisfy, we want excellent long range terminal performance without blowing things in half at close range. I'm currently using Accubonds close and Bergers far, I was hoping to give the Bergers a better test but only shot a cow elk at 335 so not a very good longrange test.
    I think one problem is there is a wide range of cals used here and what may function in one cal may not function in an other so to one guy they are great and another says they are crap and should not be used. We do not have uniformity across all cals and should not really expect it IMHO.:rolleyes:
     
  10. elkaholic

    elkaholic Well-Known Member

    Messages:
    5,346
    Joined:
    Dec 4, 2008
    There is some truth to the various caliber thing. Someone accurately pointed out the other day that a larger caliber has a better ratio of core to jacket. This does help expansion.
     
  11. Boss Hoss

    Boss Hoss Well-Known Member

    Messages:
    1,843
    Joined:
    Nov 10, 2005


    The resaon Meplats are uniformed is to try and eliminate vertical dispersion period----to try and open up the point any further is pointless and will be detrimental to accuracy. This will fall on many sets of deaf ears but it is a fact. I shoot 1K with several ballisticians and engineers (they will not do it in front of you on the phone but snicker about it in private) from 2 of the big 3 and they all concur that this activity is detrimental to accuracy.
     
  12. bigngreen

    bigngreen Well-Known Member

    Messages:
    5,839
    Joined:
    Nov 24, 2008
    Sure are a lot of BR guys selling meplat trimmers :rolleyes: I would not try to open up the hole but to give it more frontal area which will increase the resistance and get the ball rolling maybe a little better. If one can do that with only sacrificing a little BC that is OK but if accuracy tanks then that won't fly.
    Only one way to measure if there is a terminal reaction to changing it, I kinda wonder if trimming even a couple thou would give the Bergers a more even, predictable terminal responce instead of the some work some zip through.
     
  13. Boss Hoss

    Boss Hoss Well-Known Member

    Messages:
    1,843
    Joined:
    Nov 10, 2005
    You are correct ---- look at a SMK under magnification (142 6.5's and the 250 and 300 gr 338's. Notice how the tips are not consistent by making them much more so it helps to eliminate V/D but does lower the B/C slightly which is no big deal when you learn what adjustments to make.