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Thread: BUMPING THE TAPERED BULLET by Paul A. Matthews

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    Boolit Master ohland's Avatar
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    Post BUMPING THE TAPERED BULLET by Paul A. Matthews

    BLACK THUNDER NUMBER 5 – MAY 2003 page 8-9
    http://www.ssbpcrc.co.uk/index.php/b...lackthunderno5

    "The concept behind the design of Lyman’s No. 457677 and 410678 tapered bullets is two-fold: first, we wanted to get as much of the bullet as possible into the bore of the barrel before firing without the extra operation of breech-seating the bullet, and second, we wanted to get as much of the bullet as possible engraved by the rifling at the instant of firing, again without the extra operation of breech-seating."
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    Boolit Grand Master Artful's Avatar
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    http://www.midwayusa.com/product/547...in-pointed-tip

    Lyman 1-Cavity Bullet Mold #457677 45 Caliber (458-459 Diameter) 490 Grain Pointed Tip
    This is a Paul Mathews designed bullet. It is of "bore rider" design, which means the front driving bands are smaller diameter than the rear bands. This allows the bullet to be seated further out of the case to make more room for powder.It is a great BPCR design and carries a lot of lube. On a good day, I've gone ten shots without fouling out with this bullet. Most days, I only make it to eight shots before fouling takes its toll on accuracy. That's still very good with no wiping or blow-tubing.Unfortunately, not every Lyman mold in this design yields completely cylindrical bullets. I have two molds of this design and one of them makes bullets that are more elliptical than cylindrical. Thus, only four stars. Wonderful bullet design, less than impressive mold.




    PaulMathews Schmittzer. 457677 designed to be a bore rider first three rings are .450 to .451, last 3 rings run .457, .458 and .459 said to Shoot amazingly well over 70 grs of Swiss 1 1/2 FG It shows up in Lymans web site


    file:///C:/Users/DELLInspiron530/Downloads/blackthunderno5%20(2).pdf
    BUMPING THE TAPERED BULLET
    By Paul A. Matthews

    The concept behind the design of Lyman’s No.
    457677 and 410678 tapered bullets is two-fold:
    first, we wanted to get as much of the bullet as
    possible into the bore of the barrel before firing
    without the extra operation of breech-seating the
    bullet, and second, we wanted to get as much of
    the bullet as possible engraved by the rifling at
    the instant of firing, again without the extra
    operation of breech-seating.

    The first objective is accomplished by having the
    diameter of the first two driving bands just under
    that of the bore diameter of the barrel across the
    tops of the lands, and the diameter of the third
    driving band small enough so that it will enter
    the tapered leade of the rifling and contact the
    rifling there when the fourth driving band is in
    contact with the root of the rifling just ahead of
    the chamber. With the bullet thus positioned, the
    second objective is reached when the bullet
    “bumps up” or obturates and moves forward the
    width of one driving band at the instant of firing.

    At that time we have four driving bands engaged
    with the rifling instead of one driving band as is
    the case with a non-tapered bullet.

    In combination, these two factors help promote
    superior accuracy with the tapered bullet. The
    first two driving bands being within the bore of
    the barrel help to properly align the bullet before
    firing. And the simultaneous engagement of four
    driving bands with the rifling helps prevent
    torsional slippage of the bullet during its initial
    forward movement.

    For all of this to take place as planned, these
    bullets must bump up or obturate at the instant
    of firing. This means that you should be selective
    in your choice of alloy. You should avoid any
    alloy containing antimony and preferably use a
    straight lead-tin alloy of 30 to 1 or even softer.

    This is important. If you look carefully at the
    bullet, you will note that it has a very short nose,
    thus little weight up front to assist in the
    obturation process. So to make certain your
    tapered bullet bumps up at the instant of firing,
    use a soft lead-tin alloy.

    Because internal barrel dimensions, including
    chamber, throat, leade, bore and groove
    diameters vary from rifle to rifle, the as-cast
    diameters of the front driving bands are a
    compromise. For example, the bore diameter
    across the tops of the lands on my two Snoverbuilt
    45-70s measure very close to 0.4495 inch.

    You will find many other barrels to be 0.450
    inch and you will find some that will go as large
    as 0.4515 inch. To design a bullet or to make a
    bullet mould that will cover this wide a range of
    dimensions necessitates a compromise on front
    driving band diameters.

    Not only are the internal barrel dimensions
    different from rifle to rifle, you will also find that
    the as-cast diameters of the three front driving
    bands are usually a tad smaller than the design
    specifications. This is because of machining
    tolerances used in the making of the bullet mould
    regardless of whether it is a Lyman production
    mould cut with a cherry or a custom lathe-bored
    mould. No mould maker can be expected to
    produce a bullet mould without having some
    tolerance, some leeway, on the dimensions. If
    they are within half a thousandth of the specified
    dimension, they have done a good job.

    But to get the ultimate accuracy from a tapered
    bullet, you want that bullet to fit your rifle barrel
    as closely as possible at the instant of firing. That
    means that in my Snover barrels I want the two
    front driving bands on bullet No. 457677 to
    measure 0.4495 inch, and the third driving band
    to measure 0.453 inch. The last three driving
    bands will go through a 0.4575 lubri-sizing die.

    But how do you get driving bands to measure
    0.4495 and 0.453 inch when they come out of
    the mould measuring somewhat less than that?
    How do you get that perfect fit with the bore
    dimension of your barrel? And is it worth the
    hassle?

    To answer the last question first, if you are
    serious about your shooting and want to squeeze
    the last bit of accuracy from your rifle, it is
    definitely worth the extra effort to “pre-bump”
    the front three driving bands prior to lubricating
    the bullet. This pre-bumping process is nothing
    new. Members of the Cast Bullet Association
    were doing it twenty or thirty years ago to get a
    precise bore-riding fit on the nose of their
    bullets. It worked to good advantage then in
    smokeless powder rifles and it will work today in
    black powder rifles. The big difference is that we
    are interested in bumping up the three front
    driving bands on a tapered bullet where the CBA
    members were bumping up the nose diameter of
    the bullet.

    This bumping up process is done in your lubrisizer.
    And I have to say right now that the lubrisizer
    should be one of the newer models having a
    steel handle, and not one of the older ones with a
    cast iron handle. Although little pressure is
    needed to increase the diameter of the driving
    bands by a thousandth or thousandth and a half
    of an inch, a cast iron handle is not made for this
    kind of work.

    To start with, put a sizing die in your lubri-sizer
    that is just small enough to clean up the main
    driving bands on your bullet. That is, if your
    bullet casts 0.459 over the rear driving bands,
    install a 0.459 or 0.458 inch sizing die. What you
    are interested in here is to hold the bullet
    perfectly centered in the die with no wiggle
    room. I personally use a 0.458 inch die.

    Next, install a nose punch or top punch that is a
    precise fit with the nose of the bullet being
    bumped up. This nose punch must fit the nose of
    the bullet precisely in order to prevent any
    deformation during the bumping process. Set a
    bullet on top of the die and push it into the die as
    deeply as possible while still leaving the three
    front driving bands in the upper entrance part of
    the die. Adjust the bottom stop on the lubri-sizer
    to maintain this position.

    With the nose punch in full contact with the nose
    of the bullet, exert a brief, firm downward
    pressure against the nose of the bullet. Do not
    “bump” the nose of the bullet or give any quick
    thrust against the handle of the lubri-sizer.

    Merely exert a steady even downward pressure
    against the nose of the bullet. Eject the bullet
    from the die and measure the diameter of the two
    front driving bands.

    You will have to process only four or five bullets
    to determine how little pressure is required to
    increase the diameter of the front driving bands.

    And about the easiest way to determine when
    you have the correct diameter is to test the fit of
    the front driving bands in the muzzle of the rifle
    barrel. They should be a smooth even push with
    no side-to-side wobble and, in my opinion, no
    visible engraving marks of the rifling.

    Remember, you will be chambering cartridges
    loaded with this bullet in a barrel fouled with
    black powder.

    Once you have determined the proper diameter
    of the front driving bands for your rifle, you will
    want to rig some kind of mechanical stop on the
    lubri-sizer that will limit the travel of the nose
    punch and allow you to bump every bullet
    quickly and easily and exactly alike. Because of
    the differences in lubri-sizers, I can only tell you
    how this was accomplished on my Saeco.

    With a pre-bumped bullet of the correct diameter
    in the sizing die, and with the nose punch in full
    contact with the nose of the bullet, I measured
    the distance between the top of the die holding
    boss and the bottom of the nose punch ram. This
    came out to be 0.600 inch. Since the top flange
    on the die was a shade less than ¾ inch in
    diameter, I purchased a copper sweat coupling
    for ¾ inch copper pipe. From this, I had a sleeve
    made that was just 0.600 inch long and would
    just nicely encircle the die flange and set
    between the die boss and the nose punch ram,
    thus limiting the downward travel of the ram to a
    precise point. Minor adjustment of the bullet
    position within the die could then be made with
    the bottom stop on the lubri-sizer. Doing it this
    way, as long as my bullets are all of a precise
    length, they will bump up a precise amount each
    time. I mention bullet length because quite often
    bullets cast at the beginning of a casting session
    or following an interruption during the casting
    session are one or two thousandths of an inch
    shorter than normal and will not bump up the
    same, if at all.

    There you have it. That is the way I am working
    with Lyman No. 457677 tapered bullet at the
    present time. And despite the little extra time and
    effort involved, the results on the target make it
    worthwhile. This does not mean that your
    tapered bullets have to be bumped up to deliver
    superb performance.

    By all means, first try your bullets just as they come from the mould and, depending upon the internal dimensions of your rifle barrel, they may perform beyond your expectations. If, after two or three range trials you are not satisfied with their performance, then
    try the bumping up process. It might be the little
    extra that puts you over the top!

    Reprinted by permission of The Single Shot
    Exchange, 67 North Congress St., York, SC
    29745
    Excellent information
    Last edited by Artful; 06-22-2015 at 02:02 AM.
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  3. #3
    Boolit Master ohland's Avatar
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    It is a known issue with Lyman molds that you may not get to quite the Ideal bullet when you cast. For molds of current manufacture, return it. For older molds, bumping may be a reasonable way to get a better boolit.

    Ellipsoidal, now that is one heckuva challenge. Whoever figures THAT out is a Boolit God or Goddess.
    Belle, Belle, Belle!
    Purty Gu-ur-url!

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    Boolit Mold
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    Know it's an old thread but has anyone see or heard of a Lyman 457675 mold by Mathews? Looked and looked but no see.

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    Boolit Master Bad Ass Wallace's Avatar
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    I have both of the Mathews boolit molds.

    Hold Still Varmint; while I plugs Yer!

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    Boolit Buddy tmanbuckhunter's Avatar
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    If you don't have his book, Loading The Black Powder Rifle Cartridge, I highly recommend it. When I decided to jump off into the deep end with this BPCR stuff it was one of the first ones I picked up, and the information I acquired from it, as well as Pat and Spence Wolfs book has been invaluable. I can only imagine one of Pauls designs would be a great shooting bullet.

  7. #7
    Boolit Master Bad Ass Wallace's Avatar
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    This 10 shot group fired from a 40/65 Sharps with the 394gn Mathews boolit.

    Hold Still Varmint; while I plugs Yer!

  8. #8
    Moderator Emeritus / Trusted loob groove dealer

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    Somewhat related. My Swede needs to have the nose bumped a bit for best accuracy. I've also bumped in other chamberings to help fill the throat.
    The solid soft lead bullet is undoubtably the best and most satisfactory expanding bullet that has ever been designed. It invariably mushrooms perfectly, and never breaks up. With the metal base that is essential for velocities of 2000 f.s. and upwards to protect the naked base, these metal-based soft lead bullets are splendid.
    John Taylor - "African Rifles and Cartridges"

    Forget everything you know about loading jacketed bullets. This is a whole new ball game!


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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check