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Thread: Why different alloys for BP

  1. #1
    Boolit Bub
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    Why different alloys for BP

    I was wondering why BPC calls for 20 to 1, to 40 to 1 lead alloy. I have shot everything from pure lead to range lead to Lyman alloy.
    I noticed a bit of difference in the filling of the mold but accuracy seems fine.
    I size to groove diameter so bumping up does not seem necessary. Why why are the soft alloys preferred?
    Thanks
    Nick

  2. #2
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    Winger Ed.'s Avatar
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    With the slower BP speeds & pressure curves, they obturate('squish') and seal the bore better.
    In school: We learn lessons, and are given tests.
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  3. #3
    Boolit Master
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    With a well-made barrel with standard chamber and leade (and no “issues” with either), and a boolit design like the Ideal 457124 or 457125, sized a thou or so above groove diameter, you should be able to get acceptable practical accuracy out of anything that can be melted and cast: wheel weights, range scrap; whatever is most easily and economically found.

    It’s when you want the maximum accuracy potential from your rifle that you have to start worrying about the alloy it “likes.” Trick boolits with odd noses like Moneys or Postells may need a certain hardness to keep their less-well-supported (by the bore) noses from slumping to the side when the cartridge is fired and the boolit is started up the barrel. Bore-diameter paper-patch boolits, whose shanks need to slug or rivet up to groove diameter while keeping the noses on the bore centerline, seem to need a more critical balance of hardness and ductility.

    I was able to mine a military range back when I first started BPCR shooting. I would sequester the .45 hardball bullets and use the lead from those to cast my Ideal numbers and later my Paul Jones Creedmoor boolits. Whatever the alloy was, it was easily castable, soft and consistent and was very accurate in whatever I was shooting it in. Of course, all the noses were fat enough to center in the leade and bore of the rifles.

    Postell boolits, designed to load through a ring of BP crud ahead of the chamber, needed something harder, so I would cast those with the rest of the range scrap; miscellaneous Linotype and wheelweight combinations. They all worked surprisingly well. You’d have to ask somebody else about Money boolits; I’ve never gotten as good results from them as the Creedmoor design, whatever the hardness.

    Paper patch boolits seemed to operate in a relatively narrow range of hardness. There is where I finally started getting some use out of the hardness testers I’d picked up at gun shows. But in the absence of direct measurements, alloys like 16:1 seemed to cover the hardness requirement adequately. Mine have Creedmoor-type noses, though; one of the old-fashioned designs with the short, round nose might tolerate a wider alloy spread, as there is less to project out front and possibly slump.

    Nowadays, I have to mostly buy lead (*sob!*), so I more-or-less reproduce the hardball lead with 20:1. I could probably go with less tin, but it’s a simple calculation to use up the dregs of the 16:1 alloy I’ve cast the paper-patch boolits from.

  4. #4
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    Quote Originally Posted by Winger Ed. View Post
    With the slower BP speeds & pressure curves, they obturate('squish') and seal the bore better.
    So, my question is, if the bullet is already a 0.001" or greater than the hole they are going to enter, so where do you want them to squish into?
    Chill Wills

  5. #5
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    Quote Originally Posted by Chill Wills View Post
    So, my question is, if the bullet is already a 0.001" or greater than the hole they are going to enter, so where do you want them to squish into?
    Like so many other things, it doesn't matter even a little bit what I want.
    You're mileage may vary, and people are always trying to re-invent the wheel:
    But soft alloys or more or less pure Lead has seemed to work best in BP
    loads & firearms for the last few hundred years.

    When I cast for my .45-70, I put just enough wheel weights in the mix so it casts well and I get a good fill out.
    And, it has worked real well. I don't know why, but it does better than the hard alloy I use for .30 rifle.

    I just write things like that off to 'People a whole lot smarter than I am already figured this out',
    and let it go at that.
    Last edited by Winger Ed.; 09-03-2023 at 05:26 PM.
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  6. #6
    Boolit Buddy Brimstone's Avatar
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    Also with some bullet designs, the groove is engineered to partially close under ignition forces.

    The same forces that obturate a patched bore rider in a muzzle loader or breach loader, same force that obturates the .458 bullet to a .462 Trapdoor bore, also partially closes the grooves to make grease move to useful purposes rather than, as the theory goes, just rest idle in the groove towards the muzzle.

  7. #7
    Boolit Bub
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    Thanks, I get good accuracy for the ranges I can shoot. I have been digging a mountain
    of range lead. With the weight of BP bullets my pure lead is going down. I will save it for Minies and balls

  8. #8
    Boolit Master
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    Quote Originally Posted by Brimstone View Post
    Also with some bullet designs, the groove is engineered to partially close under ignition forces.

    The same forces that obturate a patched bore rider in a muzzle loader or breach loader, same force that obturates the .458 bullet to a .462 Trapdoor bore, also partially closes the grooves to make grease move to useful purposes rather than, as the theory goes, just rest idle in the groove towards the muzzle.
    I've dug a lot of boolits out of the dirt - dont see any sign of lube in the grooves - I woulda thought the rotational force would be sufficient to a) keep the lube forced against the rifling as the boolit travels downbore b) throw off any thats left on exiting the muzzle ----with all but the stickiest and hardest of smokeless lubes ......................

  9. #9
    Boolit Buddy
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    I shoot more black powder cartridge handguns than rifles. I've found softer bullets, like 1-20s in the 45 Colt cartridge, not only shoot better but do not lead the bore or even the forcing cone. That was enough to convince me.

    YMMV,
    Dave

  10. #10
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    Quote Originally Posted by fiatdad View Post
    I was wondering why BPC calls for 20 to 1, to 40 to 1 lead alloy. ............ why are the soft alloys preferred? Thanks
    Nick
    The composition of lead to tin alloy for the best accuracy depends on the bullet weight (mass), the expected velocity and whether a lubed bullet or a PP'd bullet. If shooting a lubed bullet at or over groove obturation is not an issue. The bullet will actually be less than groove diameter as it will ride over and be swaged down by the layer of lube in the barrel. However, if obturation is wanted the alloy softness needs to match the bullet weight (mass). A lighter weight bullet will need a softer alloy with a given velocity (acceleration).

    As to velocity (acceleration) bullets 400 - 500+ gr of 40-1 or 30-1 do best down around 1000 fps+/-. If pushed to 1100 - 1200 fps then a 20-1 is most often best. With velocities of 1250 - 1500+ fps a 16-1 alloy was proven the best after extensive testing by Frankford Arsenal back in 1880 - 1882. That was with the 45-70 with the new 500 gr bullet. It was found the 405 gr bullet with the 70 gr powder charge did not adequately obturate [obturation was the thought of the day as they used .459 sized bullets in .460 - .464 groove diameter barrels]. However, with the mass of the 500 gr bullet [still sized at .459] over the same 70 gr powder charge the bullet did obturate. The 16-1 alloy then gave the best accuracy. The 405 gr 45-55 carbine bullet was of a softer alloy that did allow sufficient obturation with the 45-55 load. No, the dish [it is not a hollow base], does not and is not intended to act as a hollow base as with Mine' style ML bullets.

    With all that said a 20-1 alloy is often recommended because it is useful over a broad spectrum of BPCs. It may, or may not, be the most accurate alloy in your rifle with your load. Only testing will determine the correct alloy.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  11. #11
    Boolit Master Lead pot's Avatar
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    If one would make an effort to find out what an alloy does fired with real black powder and there is a difference between powders used on how the bullet obdurates with different alloy hardness. When a bullet leaves the muzzle looking good it will shoot good if the one sending it down range does.
    The first two the left one was fired and the unfired one is the same unfired. The bullet is a 715 grain .50 cal. creedmoor nosed from a Paul Jones mould. The fired bullet has completely changed in profile and it was cast soft with 1/40 L/T and it shows signs of stripping and it shortened .097" in length.

    Click image for larger version. 

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    The 9 are all the same shot with different alloy hardnesses. The first is unfired.
    A GG hard alloyed bullet at groove diameter with a good wad under it will hold the gas back just fine because it's a tight fit on the bore.
    The Hollow point rebated hollow based bullet is one I worked with a few years back to see how a rebated boat tailed PP will perform over a flat base normally used. That bullet is a mix of 1/16 lead, tin, 5% antimony and patched to bore diameter and it filled the grooves very well. The problem with this profile design was protecting the base from damage.
    The alloy temper is a shooters choice, what ever he is satisfied with the results.
    For me 1/16 L/T or 1/18 L/T/Antimony is my choice. I only shoot the PP bullets.
    Attached Thumbnails Attached Thumbnails IMG_1489.JPG   IMG_0298 (4).jpg  

  12. #12
    Boolit Master
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    Quote Originally Posted by Lead pot View Post
    If one would make an effort to find out what an alloy does fired with real black powder and there is a difference between powders used on how the bullet obdurates with different alloy hardness. When a bullet leaves the muzzle looking good it will shoot good if the one sending it down range does.
    The first two the left one was fired and the unfired one is the same unfired. The bullet is a 715 grain .50 cal. creedmoor nosed from a Paul Jones mould. The fired bullet has completely changed in profile and it was cast soft with 1/40 L/T and it shows signs of stripping and it shortened .097" in length.

    Click image for larger version. 

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    The 9 are all the same shot with different alloy hardnesses. The first is unfired.
    A GG hard alloyed bullet at groove diameter with a good wad under it will hold the gas back just fine because it's a tight fit on the bore.
    The Hollow point rebated hollow based bullet is one I worked with a few years back to see how a rebated boat tailed PP will perform over a flat base normally used. That bullet is a mix of 1/16 lead, tin, 5% antimony and patched to bore diameter and it filled the grooves very well. The problem with this profile design was protecting the base from damage.
    The alloy temper is a shooters choice, what ever he is satisfied with the results.
    For me 1/16 L/T or 1/18 L/T/Antimony is my choice. I only shoot the PP bullets.
    Am I seeing this right? So the nose has actually subsided into the body of the boolit ?

    I tend to like soft boolits but you won me with this !!!

  13. #13
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    Quote Originally Posted by indian joe View Post
    Am I seeing this right? So the nose has actually subsided into the body of the boolit ?

    I tend to like soft boolits but you won me with this !!!
    Yup! [big grin} you go soft enough and the bullet reforms into a wad cutter.
    Chill Wills

  14. #14
    Boolit Master Lead pot's Avatar
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    LOL, even if they turn into a wad cutter they will still shoot good

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  15. #15
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    Yes! Kurt, I remember you posting that years ago go. I have always admired the lengths you go to learn, as well as share.
    Not having done that test, no wadcutters in my mold stable, I am going to guess, if you doubled the distance you shot this target, the group would look VERY different. An issue of form stability.
    Last edited by Chill Wills; 09-12-2023 at 01:31 PM.
    Chill Wills

  16. #16
    Boolit Master Lead pot's Avatar
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    Chill our right. The longer range would put those into the ground or over the hill.
    Those are swage cores I use, not cast.
    I shot a lot of bullseye with the S&W Mod 52 38 master that uses the full wad cutter and it shot very well.

  17. #17
    Boolit Master
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    I alway thought that I was using pure lead in a cap and ball gun because when loading the cylinder because the ball is just a bit bigger than the cylinder its getting loaded into and harder alloy is not necessary when shooting at the velocity that a black powder gun produces. its not like your trying to shoot at 2000 or 2200 fps when bullet sizing to bore adequate lube and even a gas check is necessary

  18. #18
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    Quote Originally Posted by indian joe View Post
    I've dug a lot of boolits out of the dirt - dont see any sign of lube in the grooves - I woulda thought the rotational force would be sufficient to a) keep the lube forced against the rifling as the boolit travels downbore b) throw off any thats left on exiting the muzzle ----with all but the stickiest and hardest of smokeless lubes ......................
    I think it depends on the lube and the velocity. I've dug a lot of bullets out of the berm with most or all of the grooves filled.
    Warning: I know Judo. If you force me to prove it I'll shoot you.

  19. #19
    Boolit Master Lead pot's Avatar
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    To settle your curiosity on how much lube stays behind in the bore and how much gets spun off the bullet just split a 20' length of 4" or 6" PVC pipe and band it back together and shoot a round through it. You will see the strips of lube stuck on the wall a and it will begin inside two feet and ends inside of 15 feet and you will see the land impressions on the longer pieces
    Or if you don't want to use the pipe just shoot over fresh snow and you will see the lube.

    Shoot into a strong wind and it ends up on your glasses and spotting scope

  20. #20
    Boolit Master
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    Quote Originally Posted by Lead pot View Post
    To settle your curiosity on how much lube stays behind in the bore and how much gets spun off the bullet just split a 20' length of 4" or 6" PVC pipe and band it back together and shoot a round through it. You will see the strips of lube stuck on the wall a and it will begin inside two feet and ends inside of 15 feet and you will see the land impressions on the longer pieces
    Or if you don't want to use the pipe just shoot over fresh snow and you will see the lube.

    Shoot into a strong wind and it ends up on your glasses and spotting scope
    learning is fun sometimes -----like Chill Wills I am amazed at the imagination - the stuff you do to figure things out - dunno how old you are but for sure there is a big kid hiding in there someplace !!!

    we shot lube cookies under the ball in a army colt one time, they turned into tracer rounds and lit the paper target on fire (not kiddin) -walker with a full charge wouldnt do it - fun but kinda hazardous in our climate

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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