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Thread: DDPP bullet finning

  1. #1
    Boolit Buddy
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    DDPP bullet finning

    Hi,
    Last year with help from fellows including Arnie, I designed a DDPP bullet for my Browning BPCR, .45-70. It was designed to be patched with BACO .0020” paper and the belted portion to be a slip fit in a fired unsized case. Brooks made the mold and it was very close, within a thousandths, of the print and the bullet drops easy from the mold. Alloy is 16:1, 83gns Swiss 1 1/2 , .065 LDPE wad, and patched to the base. BACO paper is used and the bullet is a very light slip fit in the case. Seating depth is .075” . You can carefully lift the case up by the bullet but a little shake and the case will drop away. Accuracy is sub MOA at 100 yards and opens up to 1.7 MOA at 200. Not what I would call great but not bad.
    Below are photos of the bullet along with the bullet dimensions along with the wrapped dimensions. The bore of the rifle is spot on at .450” measured by slugging at the breech end. Star brass and wall thickness at neck is .0095”. The bullet marked with a W was patched Hyde style and you can see the imprint of the folded patch in the bullet base. Both bullets fired into my swimming pool. They show a lot of base deformation, how much this affects accuracy is a guess but it can’t help. With the thin paper the base diameter is still over groove diameter by .0012” but the bore diameter size is so small I can about hear the bullet rattling down the barrel...the accuracy is minute of barn door. Loading was fiddle with this thin paper as the bullet was loose in the case.
    Thoughts?
    Cheers Richard

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    Last edited by flatsguide; 09-08-2021 at 08:14 PM.

  2. #2
    Boolit Grand Master Don McDowell's Avatar
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    Well that's the thing about paper patch bullets, there's no place for the alloy displaced by the rifling to go except over the edge of the base. So if the bullet is over bore diameter to start with then you add the paper thickness, you'll end up with what your pictures show.
    Grease groove bullets have that problem if they get to far over groove diameter, altho a lot if it is absorbed by the lube grooves.
    You may want to try a thinner paper something in the 7 lb territory to see if that finning and base cupping subside a little.
    Long range rules, the rest drool.

  3. #3
    Boolit Buddy
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    That’s the problem Don, there needs to be a match in bullet diameters, as I mentioned using thinner paper will work for the belt section then the bore section of the bullet winds up too small in diameter. Not much one can do except design a DDPP around a particular paper, preferably thin, so both bullet diameters patch to optimum size, say .451” for the bore and .458” for the belt then neck the case down to fit the belt section.
    Cheers
    ,

  4. #4
    Boolit Grand Master Don McDowell's Avatar
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    From what my rifles have told me over the years, any time the bullet before wrapping gets bigger than the bore, the more fits it will deal you.
    The two 45 caliber dual diameter bullets I shoot both are .450 on the base, and something around .454 after wrapping, both wrapped in SC 55Y. One of them shoots very well in all but one rifle, the other I'm just been running a bit this summer, and it shoots well enough out to 600 or so, and not bad but not great beyond that, and I'm thinking that's because it's just a tad long for the 18 twist. I haven't tried it in the 16 twist gun as that one is a pretty tight bore, and has a real hissy fit when the bullets get to large.
    Both of the dual diameters work in the Browning bpcr, but the newest one doesn't shoot quite as well. I'm thinking shorten the bullet up to 1.43 and it may come in like gang busters. It will shoot 3 inch groups at 300.
    I am starting to think all things considered it gets pretty tough to beat a straight sided bullet from .444 to .446 before patching, as long as the bullet length doesn't crowd what the twist will handle.
    Long range rules, the rest drool.

  5. #5
    Boolit Master
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    A couple of thoughts come to mind.
    It is noted that the bullets must have bumped up, seeing that the heretofore .450" patch to bore body is deeply engraved by
    the rifling. And, of course the "greater than bore diameter" 0.4552 base band is deeply engraved.
    -- Try sizing the base band down to perhaps 0.452-0.453"(a convenient "45 auto" sizing die size)-probably need to go to a slight taper crimp then.

    --Consider going to an alloy that will reduce bump up.

    And, of course stay with the thicker paper that gives you a good slip fit of the "patch to bore" body of the bullet.
    beltfed/arnie

  6. #6
    Boolit Buddy
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    Hi Arnie, thanks for weighing in. I’ll try your suggestion of reducing the belt dia although I was hoping initially to not have to neck the case. I’m heading in the direction to reduce anything that causes the bullet base to be deformed.By swaging the bullet down I’ll try base first then nose first and see were the excess lead goes. I have come to the understanding that any base deformities are very detrimental to good accuracy.
    Thanks Richard

  7. #7
    Boolit Mold
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    Just a thought try it with harder alloy and see what happens. nothing too lose, moezingo

  8. #8
    Boolit Buddy
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    I order my lead alloy,16:1, from Roto metals or BACO, I’m wondering now if I may have gotten a softer alloy. It sure has a lot of engraving for supposedly 16:1 I’ll break out my hardness tester and see wazzup.
    Thanks for jogging the little grey cells, as someone used to say.
    Thanks Richard

  9. #9
    Boolit Grand Master Don McDowell's Avatar
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    What do the fired bullets measure?
    Long range rules, the rest drool.

  10. #10
    Boolit Buddy
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    Click image for larger version. 

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  11. #11
    Boolit Buddy
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    Tried to rotate the info you wanted Don but no luck.
    Cheers Richard

  12. #12
    Boolit Buddy
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    As suggested I ran the patched bullets through a Lee .458” sizing die. The actual bullet diameter miced .459”. MOA groups at 200 yards. Good improvement in accuracy. Also this bullet shoots well at a thousand yards too.
    Thanks For the suggestion Arnie.
    Richard

  13. #13
    Boolit Master Lead pot's Avatar
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    Since Arnie introduced me to DDPPE bullets it raised my interest more using them. It started at Lodi during a long range match and I worked the pits at 800 yards and he was shooting one of his .40's. Shot after shot either went into the 10" X ring or just outside of it into the 10 ring and his very last shot missed the 10 ring the with of my finger. This started my interest again in the .40 caliber I made a safe Queen and I ended up having another .40-65 build.

    When I tested some rounds Arnie sent me last winter he wanted to see how his Alloy held up shot in two .40 caliber rifles, .40-65 and .40-70 in standard chambers.
    The photo's are his bullets except the .44 and the three on the far right of the 20 the last 3 are mine of a different caliber.
    With his alloy mix those bullets had virtually mo set back or finning as well as the three are also his.
    The .44 I converted from an undersized straight shank mould to a DDPP also has no finning.

    When it comes to the dual the diameter and mostly the Alloy temper/hardness is the factor, not the paper thickness. Thickness of the paper is a fix when the actual diameters of the bullet is to large or small for the groove and bore diameter. I have shot printer paper bringing the diameter of a .44 caliber bullet for use in a .45 caliber and shot just as good as thin paper for the caliber. My Friend Bill Bagwell, now at Gods side, also used printer paper a lot with very good results. match the base and shank diameter with the paper you use that fits the bore and groove diameters and a hard alloy. with a proper fit you don't have to rely on obturation to fill the grooves to seal the gas.
    Concentrate on the proper alloy and bullet design that matches your chamber and throat.
    I mix my own alloys, I learned not to rely on premixes.


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    Last edited by Lead pot; 11-22-2021 at 12:05 PM. Reason: the Mac has it's own idea what to print :D

  14. #14
    Boolit Buddy Gobeyond's Avatar
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    Obturation

    Quote Originally Posted by flatsguide View Post
    Hi,
    Last year with help from fellows including Arnie, I designed a DDPP bullet for my Browning BPCR, .45-70. It was designed to be patched with BACO .0020” paper and the belted portion to be a slip fit in a fired unsized case. Brooks made the mold and it was very close, within a thousandths, of the print and the bullet drops easy from the mold. Alloy is 16:1, 83gns Swiss 1 1/2 , .065 LDPE wad, and patched to the base. BACO paper is used and the bullet is a very light slip fit in the case. Seating depth is .075” . You can carefully lift the case up by the bullet but a little shake and the case will drop away. Accuracy is sub MOA at 100 yards and opens up to 1.7 MOA at 200. Not what I would call great but not bad.
    Below are photos of the bullet along with the bullet dimensions along with the wrapped dimensions. The bore of the rifle is spot on at .450” measured by slugging at the breech end. Star brass and wall thickness at neck is .0095”. The bullet marked with a W was patched Hyde style and you can see the imprint of the folded patch in the bullet base. Both bullets fired into my swimming pool. They show a lot of base deformation, how much this affects accuracy is a guess but it can’t help. With the thin paper the base diameter is still over groove diameter by .0012” but the bore diameter size is so small I can about hear the bullet rattling down the barrel...the accuracy is minute of barn door. Loading was fiddle with this thin paper as the bullet was loose in the case.
    Thoughts?
    Cheers Richard

    Click image for larger version. 

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    Is that the obturation of the bullet we’re witnessing?

  15. #15
    Boolit Buddy
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    I think so Gobeyond

  16. #16
    Boolit Buddy Gobeyond's Avatar
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    Quote Originally Posted by flatsguide View Post
    I think so Gobeyond
    Thanks, more variables!��*��

  17. #17
    Boolit Man
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    Quote Originally Posted by flatsguide View Post
    That’s the problem Don, there needs to be a match in bullet diameters, as I mentioned using thinner paper will work for the belt section then the bore section of the bullet winds up too small in diameter. Not much one can do except design a DDPP around a particular paper, preferably thin, so both bullet diameters patch to optimum size, say .451” for the bore and .458” for the belt then neck the case down to fit the belt section.
    Cheers
    ,
    This is the same problem I had with a DD bullet from a mold I had made for my 38-55. The problem may have stemmed from my bore/groove measurements being off a bit. This same bullet shoots very well in another rifle that I know of. These DD bullet shoot beautifully when perfectly fit but I tend to agree with Don’s thoughts on straight sided bullets. It seems much easier to get the perfect fit just by experimenting with different paper.
    I gave up on the DD bullet and sold the mold. The rifle is shooting very respectably with black or smokeless, using a groove sized patched bullet. I plan to try a bore sized bullet for black only, as soon as I decide on a mold.
    JKR

  18. #18
    Boolit Grand Master Don McDowell's Avatar
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    I get pretty decent results with dual diameter bullets that the base band is bore diameter and 1 caliber long, with the base of the nose .005 under bore diameter, and wrapped in thin paper. Also looking like a single .060 wad between the powder and bullet.
    16-1 looks to be about as good as it gets for alloy.
    By the time the smoke is cleared at Phoenix week after next guess I'll know more about my theory.
    Long range rules, the rest drool.

  19. #19
    Boolit Master semtav's Avatar
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    Quote Originally Posted by JKR View Post
    The rifle is shooting very respectably with black or smokeless, using a groove sized patched bullet. I plan to try a bore sized bullet for black only, as soon as I decide on a mold.
    JKR
    What are your barrel dimensions and bullet dimensions on your patched to groove adventure. And bullet alloy?

  20. #20
    Boolit Master Lead pot's Avatar
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    Studding bullets has been my interest since age 12 and it's still an interest with me at 83. It's a winter past time for me when it's not fit for the range time.
    Lately the DDEPP bullets Arnie designed caught my interest also and I have a couple moulds that I had made and a couple I changed the straight shank PP bullet mould to a DD.
    When Arnie sent me some bullets he case they were shot into the snow bank to see the effect of the alloy shot through two different .40 caliber rifles and also some I shot with a .38-50 and .44-77 as well as the .44-90 BN. These rifles have the standard chamber end transitions of the now used 45º and the original shallow tapered funnel transitions of the original rifles and OI will say that I have not found any recovered bullets that had Finns.
    My finding with the cause of finns is a loose chamber.I have a couple rifles that have a generous chamber and those rifles I have recovered bullets that have finns and it made no difference if I used alloy from 1/16 to 1/30 as well as some with 1/14.
    The issue is the bullets obturation. When the bullet expands in the large chamber it gets set back filling the excess space and this gets ironed back down when that obturation gets ironed back down as the bullet entered the throat and gets pushed back towards the base. The alloy temper does make a difference reducing the finns to a degree, but it's not a 100% cure for oversized chambers.
    Below are some DDEPP bullets shot in my rifles and none have a Finn problem. But my chambers are what I call the original lead bullet chambers of old.Some with 4º transitions and some with the 45º.

    These are the bullets Arnie sent me and they were fired in the Shiloh .40-70 with a standard 45º chamber and a Browning BPCR .40-65. It's hard to see the bullet bases in this photo but the bases are clean and they were cast using Arnies hard alloy.
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    Here are some DDEPP I shot with my .38-50 Rem Hepburn and .38-50 CPA. I did not get enough snow this year for a good value tests with alloys but no finns on the few I shot this winter.
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    Also here are straight shank PP and a couple GG shot that have clean bases of several different alloy mixes.
    The chamber size and bullets not oversized for the groove diameter. It's mostly alloy temper with large chambers that causes the finns.

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    Hey, I don't just look at a dozen test bullets to see the effect of why did that bullet go in the dirt or where did that one go LOL. These are 3 pound coffee cans full of test bullets shot over a couple cold winter days that got melted back down into ingots

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