Hey BRENT!!! and others I need some advice!!

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by *WyoWhisper*, Feb 27, 2004.

  1. *WyoWhisper*

    *WyoWhisper* Guest

    OK... I'm not sure what to think of this...

    with all the talk of meplat uniformity I had to have one! So i purchasedone and have been playing with it a bit...

    It make sense that it should keep things more consistient..

    OK so I fire my original groups 3 days ago..
    my 308 is shooting the 175 SMK at 2725 fps...

    at 750 yards it is about 20 MOA ..

    Now yesterday... I needed 28 MOA same load as before same bullet but I uniformed the meplat.. I didn't take A LOT off the tip, at least I thought...

    has anyone experienced this? Just seems a little weird to me.
    That took the B.C from .505 to .340!!!!
     
  2. jb1000br

    jb1000br Well-Known Member

    Messages:
    1,307
    Joined:
    Jul 8, 2003
    Did you steel wool the outside burr off the tip created by the end mill?


    BTW If anyone is interested, A guy from Williamsport is starting his own shop and making similar meplat uniformers to the one tooley makes--Only one step better!!

    I will be getting these to try in a few days and will post pics.

    It has another tool to remove the bur from the inside of the bullet tip, instead of forcing that chunk of copper in the hole, this clears it out.

    Also there is no plastic on it like tooleys tool--all steel!!

    He will be selling them for about the same price as tooleys, but you get the extra part to clean out the tip.

    EMAIL ME IF YOU ARE INTERESTED

    JB
     

  3. MAX

    MAX Well-Known Member

    Messages:
    263
    Joined:
    Sep 10, 2001
    Wyo, I have no experience with the tool, but meplat size has a LARGE influence on BC. Approx 70% of a bullets "sleekness" comes from nose shape, and much of that portion from meplat width. It is I think, a shock wave multiplier, ie. when you double the meplat width from say .005" to .010", the drag increase is geometric rather than linear. Hence, the big change in BC you experienced. It is the devil's brew I suppose; you may improve BC uniformity but at what expense?

    ON the other hand, I may be totally out of my mind on the subject. [​IMG]

    [ 02-27-2004: Message edited by: MAX ]
     
  4. JD

    JD Active Member

    Messages:
    37
    Joined:
    Feb 28, 2003
    There's a post on Benchrest.com about this topic. Someone said if you trim too much of it, it lowers the BC as youve experienced. Look under 1000yd BR, and look for the topic of "who trims meplats". Hope it helps. JimD
     
  5. Boyd Heaton

    Boyd Heaton Well-Known Member

    Messages:
    1,071
    Joined:
    May 14, 2001
    IMHO........Don't worry about trimming them.If it aint broke,don't fix it.
     
  6. BountyHunter

    BountyHunter Writers Guild

    Messages:
    4,803
    Joined:
    Jun 13, 2007
    jbr1000

    Not sure what tooley tool you have, but the two I have are all steel. Sure it is a tooley?

    Plus the pictures on the thread about the Tubb tool show it steel and it is made by Tooley only sold by Tubbs.

    BH

    [ 02-27-2004: Message edited by: BountyHunter ]
     
  7. *WyoWhisper*

    *WyoWhisper* Guest

    Brent,
    I went from .060ish to .080ish

    the 21 MOA was shot on a bright sunny day

    the 28 MOA was shot on an overcast ugly day

    just find it hard to believe...

    JB no burs on the tips everyting was/is smooth...

    ???????? [​IMG]
     
  8. ewallace

    ewallace Well-Known Member

    Messages:
    991
    Joined:
    Mar 17, 2002
    I have used the meplat tool that Dave makes but did not notes that much of a difference and we were shooting a mile with the 300g SMK. Try shooting them in the same conditions back to back and see if it was conditions [​IMG]
     
  9. Brent

    Brent Well-Known Member

    Messages:
    2,537
    Joined:
    Jun 12, 2001
    Ric,
    What was the temp and BP for for both days?

    DO you measure it with a Kestrel 4000 or by some other means?

    Michael and I were out on the river bar shooting, maybe a month ago or so, I don't rember the specifics, he may, but I remember the density altitude was way down below -5000 ft. I think I was shooting low and I couldn't understand why, but I didn't see the minus in front of the 5000 ft. I just saw 5000 ft the first time I looked at it and went back to it for another look when that made no sense what so ever, whould have been hitting way high at 5000 ft.

    Just a stab, but maybe an overcast low pressure system the first day when you were hitting high, nice blue sky high pressure day after you trimmed them meplats?

    If you can, tell me the meplat diameter, before and after and I'll see how much this RSI program say's it will change the BC, and by what extent the drag is increased on the meplat.

    To figure your .340 BC, were you just manipulating it down until you connected POI with POA with the firing solution this time?
     
  10. Brent

    Brent Well-Known Member

    Messages:
    2,537
    Joined:
    Jun 12, 2001
    Just fir kicks and giggles, I changed the tip diameter for the 210 JLK from .060" to .070" diameter to compare the BC's predicted. Started out at .670 BC, down to .645 BC.

    I don't imagine you cut the tips back so far the diameter increased much more than .010", or if that much, so I'm guessing the BC change was air density, posibly in combination with uniforming the meplats?