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Thread: my thinking about "soft casts".

  1. #1
    Boolit Master
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    my thinking about "soft casts".

    hello ,

    i was reading some posts regarding the hardness of the castboolits used.
    most of them was trying to get the alloy harder by dropping WW in cold water , age hardening and different additives.

    i do believe these "hard cast "boolits have a place in reloading , if one is a commercial caster and the boolits have to be shipped
    the hardness will help to get the boolits undeformed to the customer.
    another reason would be if one shoots these boolits at high speed [ read high pressure ] naked and lubed .
    the soft alloys would loose grip and skid through with no rotation because they would be to soft to firmly hold the rifling.

    but....
    we are no commercial casters , and we don t shoot our boolits naked and lubed .
    we paperpatch our boolits !

    i am very sure that our paperpatch follows the rifling perfect if the patch is firmly compressed
    i have done some experimenting with different coresizes in the 6,5x55 mm cartridge , the rifles in this caliber have a fast twist.

    my alloy of choice is a pure lead with some tin mix , i think the BHN would be somewhere about 8 or 9 BHN .
    this leaves me a soft and ductile core that i run through my sizer ... 0.264 , thats full diametre for this caliber.
    then i wrap them twice in chainbar printerpaper , and when they dried i run them through the same sizer again.

    the patch gets "ironed" really thight to the core this way and is more than capable to grip the rifling.
    now for the ductile part , wich is a great bonus in my opinion.

    cores in these soft alloys are easily bent by hand , but wil not tear or break , one could twist a circle with them if wanted .
    so , when the primes fires and the powdercharge ignites there will be a sudden pressure spike.
    our boolit has a certain mass and due to inertia it doesn t want to move instantly , the base of the boolit wants to move faster than the nose , and will continue to do so as long there is pressure behind it.

    this leaves the conclusion that the soft boolits will deform under pressure .

    this deformation can only be in diametre and is restricted by the barrel , wich is exellent for our purposes.
    the boolit will form itself to the barrel and rifling under this pressure , and will continue to do so untill it leaves the barrel.
    our very compressed paperpatch is though enough to follow the rifling and not skid through it , and is assisted by the fact
    that the boolit grows in diametre thus is pressing hard against the walls of the barrel for an exellent gassealing .

    to a certain point this thinking would suggest that the bigger the pressure behind the boolit is , the harder the boolit
    will press against the walls in the barrel .
    so , now the speed-limit of this bullet will only be restricted to the point that our heavily compressed patch would loose its grip
    on the rifling and skid through.... and this is a very strong patch .

    oh... one more thing
    if our boolit is deformed and this deformation is restricted [ barrel-walls ] our boolit material gains strenght , because the molecules
    of our alloy get compacted together...
    don t know if i put that correctly , in dutch language i could describe it better ...

    what would you say .. am i thinking in the right direction ?

  2. #2
    Boolit Master Dan Cash's Avatar
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    The inertial deformation of a very soft bullet will continue after the bullet leaves the bore. At what pooint the hardness of the alloy prevents this, I do not know. The longer the barrel, the less this post departure deformation occurs. See: The Bullet's Flight; Mann. He demonstrated this, complete with pictures.
    To paraphrase Ronald Reagan, the trouble with many shooting experts is not that they're ignorant; its just that they know so much that isn't so.

  3. #3
    Boolit Master bullbarrel033's Avatar
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    Do your tight patches leave the bullet at the muzzle?
    THE ONLY WAY YOU CAN HIT THE CENTRE OF THE TARGET IS WITH A CENTREFIRE!!!

  4. #4
    Boolit Master 303Guy's Avatar
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    I have been thinking that a softer alloy may be beneficial in paper patching. I've found that it takes more pressure/velocity to disintegrate the patch with a softer alloy. The core conforms to the rifling better. I'm not sure what the downrange effects may be though.
    Rest In Peace My Son (01/06/1986 - 14/01/2014)

    ''Assume everything that moves is a human before identifying as otherwise''

  5. #5
    Boolit Master
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    hi dan ,
    thats interesting , i didn t know that .
    let me think about this , the boolit deforms inside the barrel due to the pressure that is pushing it .
    this will create tension as the boolit can not expand more than the inside of this barrel.
    when the boolit leaves the barrel there is no more pressure behind it , but there is also no barrel to restrict the expansion , so my guess would be that the tension on the boolit gets relieved after it leaves the barrel , so mabey a slight increase in diametre.

    after this happens the boolit is tension-less and the only forces working on the boolit will be gravity , air friction and centrifugal forces.
    the gravity will not be of great concern in my opinion , the air- friction can be lessend to an exeptable level by choosing the boolit-style
    but the greatest power working would be the centrifugal force...
    if the boolit is somewhat out of round , it could fly anywhere.
    this would be another advantage for the soft-casted boolits , remember they deform to the barrel , wich is perfectly round .

    i have to think this over a little more i think ..

  6. #6
    Boolit Master
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    hi .303

    yes , i did have to use a little more powder , read more pressure , to get the patch to shred into tiny pieces
    since i patch the full-bore cores in this soft alloy .

    i went from 19,5 gr to 20 gr of lovex D060 powder [ = AA5477 ] , so it didn t take that much .
    the patch shreds at the muzzle and leaves me a fine "pulp " , i think that is the best description for it .

    i will continue testing this load , but it seems to be accurate enough !

    so yes bull... the patch schreds at the muzzle .

    think with me for a while here .303 ,

    we have the suggestion that a soft-casted boolit will expand under pressure , and that this expansion is restricted by the barrel.
    when we would size the core at bore-size the core could expand to groove-size minus the thickness of the paper fully compressed.
    so the amount of expansion would be much greater than with a core at full groove size , in other words , the boolit
    will be a lot less strained if it is not sized at bore-size.
    first , the cores dont undergo the stress of sizing before the patch is applied , and second , the boolts cannot deform
    as much inside the barrel , because the are simply larger.

    i can see some real benefits here , like to hear your opinion on this subject .

  7. #7
    Boolit Master 303Guy's Avatar
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    Hi Edwin.

    I'm going to have to think on this for a while.

    I wouldn't worry about boolit deformation as it leaves the muzzle if accuracy is good. It would depend on muzzle pressure which should be low enough with only 20 gr of powder.

    I was using quite a soft alloy and with one gun and was getting MOA accuracy with open sights. I was using less powder than you but with a fibrous filler (wheat bran) which raised chamber pressure but lowered muzzle pressure (less muzzle blast) but my barrel is short (carbine).

    The way I have been sizing my patched boolits is a firm fit in an unsized neck and the nose section tapered to engage the leade on chambering. The boolits get swaged into the bore. To overcome trailing edge feathering I made the boolits with a small chamfer on the base.



    But here the soft alloy still got hammered.



    Here is a soft core fired with about 2 gr shotgun powder.



    Patch still intact through a bunched up rag and rubber grounds. It may have stopped in the rags - it was pretty slow.
    Rest In Peace My Son (01/06/1986 - 14/01/2014)

    ''Assume everything that moves is a human before identifying as otherwise''

  8. #8
    Boolit Master 303Guy's Avatar
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    Just a thought - the black powder guys with 45-70, load to bore size and the boolit bumps up to fill the grooves on firing (I'm open to correction). Some of these guys are shooting 800 yd gongs with them.
    Rest In Peace My Son (01/06/1986 - 14/01/2014)

    ''Assume everything that moves is a human before identifying as otherwise''

  9. #9
    Boolit Master
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    First the black powder crowd sizes to bore size because of the fouling that accumulates in the barrel, and throat following repeated firings.
    Secondly black powder explodes it does not burn like the smokeless that we use. This delivers a greater or more violent "kick" to the bullet aiding in its expansion to grove diameter. Or at least that is what I have been told repeatedly.

  10. #10
    Boolit Master kens's Avatar
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    in your original post you say the bullet grows in diameter, I beg to differ.
    If you are sizing to .264, then the bullet is actually getting squeezed into smaller diameter, the bore of 6.5x55 is .256 and the groove is .264.
    You are taking a .264 bullet and squeezing it into the ..256 lands.
    The bullet is growing in length because it is getting squeezed into the .256 lands.

  11. #11
    Boolit Master kens's Avatar
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    Quote Originally Posted by 303Guy View Post
    Just a thought - the black powder guys with 45-70, load to bore size and the boolit bumps up to fill the grooves on firing (I'm open to correction). Some of these guys are shooting 800 yd gongs with them.
    No, they are loading just like any other cartridge, they load and size to GROOVE dia, more specifically the throat dia.
    The muzzle loader black powder guys load to BORE dia. and then 'bump up' to groove dia.

  12. #12
    Boolit Buddy
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    I may be wrong, but I think expanding is the wrong word and thus misleading as to what the boolit does. When you blow air into a balloon, it expands. When a boolit is fired I believe it is deformed from its original shape and formed to the shape of the groves and lands and not compressed. It probably gets a little longer, but I don’t believe it expands when leaving the barrel.

    The most serious muzzle loaders I know only use only 100% lead balls, so when fired, the lead “obturates” to make tight seal with the barrel.

    It might be an interesting experiment to measure the length of a boolit before and after it is sized to see if it grows in length. This might need the percision of micrometers to see any change with sizing.

  13. #13
    Boolit Master 303Guy's Avatar
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    I have samples of fired boolits that have lengthened by being squeezed down in the bore.
    Rest In Peace My Son (01/06/1986 - 14/01/2014)

    ''Assume everything that moves is a human before identifying as otherwise''

  14. #14
    Boolit Buddy
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    This is an interesting slow motion video of a paper patched boolit being fired if you haven’t already seen it.

    https://youtu.be/7XT9Cekqb_M

    To me it looks like the centrifugal force causes the patch to come off. Plus maybe friction of the air.

  15. #15
    Boolit Master
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    Greg: I really enjoyed that vid. Very interestng.
    303 Guy: As I am sure you know, and maybe even agree with me, the most accurate cast bullet you can shoot is one that fits the throat of the chamber. This bullet will of necessity size down to groove size of the barrel upon firing. The throat sized bullet is most accurate because it has less room to slop around in and is most likely to be best centered on the bore of the barrel. Brodie

  16. #16
    Boolit Master
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    mabey the language limits me somewhat..

    my thinking would be that a soft-alloy casted is easily deformed under the applied pressure of the ignited powder .
    i would say that this boolit would expand in diametre , but of course there is no room for this expansion inside the barrel , thus the paper gets squeezed between the boolit-core and the barrel for an exellent gasseal.

    when a material gets squeezed in a mold , the material gains strenght due to the compression of the molecule-structure.

    so... an unsized core at groove-size is a much tighter fit than one at bore-size .
    the one at boresize has to expand more for the same pressure on the barrel-walls due to its smaller diametre.
    this leaves me the idea that the unsized-core bullet will be less strained than the bore-sized core , and hold its original measurements better.

  17. #17
    Boolit Master Good Cheer's Avatar
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    You have to develop the load to suit the firearm being used.
    If you can make soft work then it works.
    My big brother's 45-70 smokeless powder hunting load is swaged soft lead 500 grains spitzers (nine pound 25% rag content) at around 1800FPS. Not unusual for him to shoot sub-MOA at a hundred.
    Mom and Dad should have named him Timex.

    A project in the works if to see if soft lead will work in a 9.3x74R... when there's time.

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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