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Thread: General mould/boolit design for rifle

  1. #21
    Boolit Master
    Rcmaveric's Avatar
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    Quote Originally Posted by John Boy View Post
    popper - books have been written and bullet designs tested extensively in different twist ratios. To consolidate all this information, there are calculators and based on inputs, the bullet with the highest SG or SF for Stability Factor is the bullet of choice. Don Miller's & Powley's are a couple. Here's Miller's
    accurateshooter.net/Blog/millerformula.xls
    From my understanding those excel file (I have it) and Powley's pocket computer were designed around copper jacket bullets. True, bullet stabilization is equally as important, but with cast bullets so is fit. Now the question is how much fit is necessary? Would love to read a good research article about bullet designs, seating methods and bullet "fit" methods.
    "Speak softly and carry a big stick; you will go far."
    ~Theodore Roosevelt~

  2. #22
    Boolit Master popper's Avatar
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    Would love to read a good research article about bullet designs, seating methods and bullet "fit" methods.
    Me too. This is what I'm trying to learn but not finding much. I know about powley/miller stuff.
    Whatever!

  3. #23
    Boolit Master
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    The nerd in me and my tendency to ponder cant help but wonder if those groves up a pope bullet disrupts airflow like the dimples on the golf ball and also lead to its increased accuracy. If you size that bullet you just uniformed its sizing bands taking away from its stepped bands.

    I did just get Dr. Manns book to read though.
    "Speak softly and carry a big stick; you will go far."
    ~Theodore Roosevelt~

  4. #24
    Boolit Master
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    https://castbulletassoc.org/blog/art...ple-techniques Para graphs 13-15 talk about fitting the throat.

    https://castbulletassoc.org/blog/art...rding-accuracy Only mentions slugging the barely.

    https://castbulletassoc.org/blog/art...-the-9mm-luger First article I have found where it talks about leade seating. I need to read the article a few more times when not half asleep.

    https://castbulletassoc.org/blog/art...-bullet-design Food for thought.

    Off topic but https://castbulletassoc.org/blog/art...-on-gas-checks This article makes actually ponder what makes an accurate bullet.

    Various articles from most cast bullet manuals and books and articles, they always talk over .002 over groove or throat diameter. I have read other opinions about sizing to bore diameter but that was just passing. I haven't found an article yet that talk about it from a reputable source. Seating depth is matter of choice from seated into the lands to .002 off the lands, to even adjusting bullet seating depth to fine tune a load. I would have to fish up the article were it talks about where a small jump is more accurate than set into the lands. It has to do with the high pressure spike on the base where a jumping the throat is more gentle and less upsetting to the bullet base. Which goes back to Dr. Manns theory. With that thought in mind, would ball seating then be short changing your accuracy potential. Even in my 9MM Luger I seat .002 off the lands and produce respectable/repeatable accuracy.

    All in the search of the golden most accurate bullet. I found various articles that talk of bearing surface. I cant help but to think design from the driving band forward is purpose driven. Do you want it to kill something, do you want to punch paper or do you want to hit long range targets or do you want a happy medium of knock down verses medium range. Ojive down is what makes it accurate. Bearing surface and the bullet base. I think we may be over thinking this bullet design. Any design that will offer adequate bearing surface with a sharp driving band and sharp base will produce accuracy. Next step of accuracy is loading techniques, what methodology/(or mythology) are you using to minimize the damage to the bullet when it jumps the throat and travels down the barrel. Use a slower powder, longer barrel, and slower twist. Maybe accuracy is a puzzle that needs to be solved for a particular bullet and barrel then mix and match till you get an accurate fit and load.
    "Speak softly and carry a big stick; you will go far."
    ~Theodore Roosevelt~

  5. #25
    Boolit Master popper's Avatar
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    Maybe accuracy is a puzzle that needs to be solved for a particular bullet and barrel then mix and match till you get an accurate fit and load.
    Exactly what I'm trying to avoid. Consider alloy as really heavy modelling clay. When fired, it squishes into the space between the mouth and throat, fills the throat, and (if a bore-rider) into the grooves and bore. If a pointy boolit the nose can slump anywhere. Bama shows a concentric boolit helps. The question is how much does the aloy get 'torn up' or mangled when firing and can we design a boolit that reduces any problems. And doesn't have to be 'fitted' to the rifle. I'm proposing an 'almost' bore rider with an alignment ring on the nose. Tapered seat between drive band and nose ogive. Sized to the smaller part of the throat to prevent jams.
    Whatever!

  6. #26
    Boolit Master
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    Sounds very plausible. I am curious. Or several thin bands to act as gas seals and a guidance system. My only comcern is an ease of chambering in a variety of rifles. Several thin rings that are tapered would ingrave easier on chambering.

    Sent from my SM-G925T using Tapatalk
    "Speak softly and carry a big stick; you will go far."
    ~Theodore Roosevelt~

  7. #27
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    NEI used the DD rings on their noses. It was a band aid for poor fit.
    A deplorable that votes!

  8. #28
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    It was a band aid for poor fit Poor fit or 'general' fit? Any links to NEI moulds and results? Choices seem to be - chamber cast and get a 'special' mould to fit a single rifle or guess and hope for the best? So far I guess I've been lucky in choices but wondering if there is an approach that will give general good results. I'm kinda thinking the 30xcb with reduced nose dia. ( I coat vs lube) and a 'guide' ring that fits into the lands. I size the drive bands to fit the throat. I shoot ARs and avoid seating touching the bore, I'm thinking longer to increase BC but mag length eliminates a long bore rider. I could size a small nose ring with little trouble. Bama's approach is great but I don't have that capability.
    Whatever!

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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