trimming the bullet meplay for better BC

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by DANTEC, Nov 25, 2003.

  1. DANTEC

    DANTEC Well-Known Member

    Messages:
    390
    Joined:
    Jul 6, 2002
    anyone have try or test to trim the bullet meplat ( with a lathe or a small tool as Tooley tool ) in the aim to get more constant BC and less elevation defect at long range ?

    good shooting

    DAN TEC
     
  2. Steve Shelp

    Steve Shelp Well-Known Member

    Messages:
    351
    Joined:
    May 3, 2001
    Dantec,
    I've been busy at work and haven't followed the message boards hardly at all in the last month or so. Don't know what you've read or been told on this.
    I've been using one of Dave's meplat trimmers (one of his first prototypes) for 2+yrs now. We also have tested plastic tipped bullets that we assembled at his shop. It's an ongoing experiment and we have tested using an Oehler M43 at 300yds to measure BC dispersion with "untrimmed meplats", "trimmed meplats", and plastic tipped bullets out of the same rifle at the same time back-to-back to give us hard numbers to go by. The M43 has the acoustics screens setup to measure time of flight and actual BC numbers for every shot fired. I can't argue with the numbers/results anymore. It's clear the trend is in the right direction and that is reducing vertical dispersion.
    By doing this you are not going to make a good rifle into a great rifle. But you will do away with unexplained flyers and help your group become rounded rather than the vertical we normally see when scoring 1000yd BR targets.

    Hope this helps,
    Steve

    [ 11-25-2003: Message edited by: Steve Shelp ]
     

  3. Brent

    Brent Well-Known Member

    Messages:
    2,537
    Joined:
    Jun 12, 2001
    Steve,

    Have you guys experimented with cutting the tips way back, or just enough so they all clean up square vs. the wild uneven ones etc.

    Have you played with boring the HP out larger and it's effects either?

    Do the really wildly uneven tip always reduce BC by a certain amount?

    Have you all established a baseline BC ES for the squared tiped bullets and compared them to the ES of random selected out of the box bullets?

    Sorry for the twenty questions. [​IMG] I never thought of testing this, but the SMK's especially are definitely pretty whacked in this area.

    I'm curious, do you guys leave the acoustic target set up, or use a stand for it that is always a set distance from the bench?

    I don't have this type of permanent setup, it's a real PITA to get accurate measurements without this.

    As I'm sure you're aware of, the distance is very critical for absolute BC numbers, relative ones for tests like you're doing would be easier, if that's all you were after.

    I usually measure from the frame it's taped up back to the front of the bench, then subtract from this the distance the muzzle of each rifle stick out beyond the bench.

    Do you guys use a seperate frame for the acoustic target just ahead of another target frame to icsolate the sound traveling through the frame. It does travel faster through the wood than it does through the air, and often the target backer material will transfer this noise to the sensor before the mach wave reaches it.
    The sensor will sometimes trigger too soon in this case.


    .....


    A side note on the acoustic target:

    I learned something you might find handy if you ever think you might be having a problem with a sensor not functioning. If you have access to a 35P you can plug the acoustic leads into, tapping the white plastic of the sensor with a fingernail should trigger the printer to print. If it doesn't it isn't working. You have to plug each sensor into the "on" plug in on the 35P (left plug on the 35P) and test one at a time tho. It will just print zeros, but the sensitivity of the sensor can be verified this way.

    [ 11-25-2003: Message edited by: Brent ]
     
  4. a.JR

    a.JR Well-Known Member

    Messages:
    98
    Joined:
    May 28, 2003
    Dantec,The 3 targets in the photo are from our recent 500 met State Champs i shot .....The one in the middle was shot with Meplat uniformed 187 BIBs and the other 2 without.....The small group target (1.230 ins) was also the 1st target of the day in the best of the average conditions offered,since building the new gun i used i have not had 1 day i could call good conditions to test properly in so i can't say for sure it's worth the effort ,But it looks promising so 1 will continue testing....I made my own Meplat uniformer because it's not exactly just down the road for me to buy one living in Australia..JR... [​IMG]
     
  5. Brent

    Brent Well-Known Member

    Messages:
    2,537
    Joined:
    Jun 12, 2001
    Nice groups Jeff! What's that you were shooting?
     
  6. daveosok

    daveosok Guest

    Where is the datum point referenced from to cut the meplat?
     
  7. a.JR

    a.JR Well-Known Member

    Messages:
    98
    Joined:
    May 28, 2003
    Brent,The match has originated in Canberra Australia ,it's called the "Fly Shoot".....Started at my range some 2000 miles north of there in 1993 .....Only shot at 500 met,quite a challenge really ,it's the only shoot i know of to join score and group together for a total:-i.e. take the middle target ,it has 4 of 10s and 1 of 8 so subtotal 48 + 9 points for the group with 1 shot through the FLY for a total of on that target of 57.1 out of a possible of 60.5....The points for group are 10 for sub 1 inch group on down to 1 point for a up to 10 inch .Groups on the 3 targets are 1.230 , 1.91 , 2.40, there is 2 more targets from this match i could not in the photo and they were the worst ones shot in the mirage ,the 5 targets together give a 5 shot x 5 targets Agg of 2.95 ins...Clear as mud i guess,hope this helps..JR..Jeff Rogers ..ps on our range we have a cash prize of $1000 for first 5 shots in the FLY
     
  8. DANTEC

    DANTEC Well-Known Member

    Messages:
    390
    Joined:
    Jul 6, 2002
    Thanks for your imput , I have set up a tool to trim the meplat and start to make experiment at 1000 yards ( our shooting range allow 3200 meters of shooting range ...)

    To Brent

    I use vibration pannel rather accoustic target , vibration pannel are made with sismic detector from miltary surplus glue on pannel ( 2 pannel spaced with 1 meter ) and a HP counter 5334 purchase from surplu stoo that less costly than a new Oeheler with accoustic target , you can use too contact pannel made with 2 alumiun foil stick on cardboard that primtive set up but that work fine for a low cost

    good shooting

    DAN TEC
     
  9. Brent

    Brent Well-Known Member

    Messages:
    2,537
    Joined:
    Jun 12, 2001
    Jeff,

    I should have said, what's that rifle you were shooting? [​IMG]

    I didn't catch the fly on the bull there at first, was just looking at them tiny groups. [​IMG]


    Dantec,

    How exactly does a vibration pannel work? Any pictures of one?
     
  10. a.JR

    a.JR Well-Known Member

    Messages:
    98
    Joined:
    May 28, 2003
    [​IMG] ....................Brent,Pic of the cartridge i designed ,the 300 redneck.It's slightly shortened 300 win mag with a .340 long neck,35 deg shoulder with standard body taper....Pictured with a std 300 win case ,don't know if the pic is clear enough to see the modified Meplat..JR
     
  11. a.JR

    a.JR Well-Known Member

    Messages:
    98
    Joined:
    May 28, 2003
    Brent ,Also pic of my home made Heavy gun..JR [​IMG]
     
  12. sscoyote

    sscoyote Well-Known Member

    Messages:
    1,255
    Joined:
    Feb 26, 2003
    If you guys don't mind humoring a novice what exactly is trimming the meplat?-- Are you guys actually shortening the bullet by taking a measured section off the tip?? If so wouldn't that lower the B.C. as well??
     
  13. ewallace

    ewallace Well-Known Member

    Messages:
    991
    Joined:
    Mar 17, 2002
    sscoyote
    When trimming the meplat you remove just enough to make the tips of the bullets the same making for consistent BC. Important in competition.
    Crow Mag
     
  14. a.JR

    a.JR Well-Known Member

    Messages:
    98
    Joined:
    May 28, 2003
    The reason i started to modify the point(meplat) was to reduce the amount of batches i end up with...To start i get as many bullets i can (500 to 1000),sort into Aol batchs of 5 thou ie #1 lot 1.325 to 1.330 and lot #2 1.330 to 1.335,i throw the highs and lows in the fire form/fouler bin then cut off the tips until i have 2 only batches of the same length ...I then put each bullet into a device i made that looks like a pencil sharpener with an adjustable stopper on the meplat end ,then u turn the bullet by hand and the cutter makes the meplat dia uniform....This is of coarse after they have been classified into lots for base to ogive length,bearing surface length and weight..Many hours later i hope i got best i can..JR ..Jeff Rogers.. pic of bullet uniformed next to one straight from the box [​IMG]