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Thread: 45-70 duplex loads

  1. #1
    Boolit Master
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    45-70 duplex loads

    Well I'm going down the black powder path. Just bought a Hepburn In 45-70. I'm wanting to shoot duplex loads. Just want to make sure I can compress a duplex load.

    My next question is what powder do I use?

    If some of you don't mind post your 45-70 Duplex loads.
    " If you cant do it with a 308 , you dont need to do it!

  2. #2
    Boolit Master
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    You don't need to compress a duplex load but just enough to hold it in place. 1/16 should be more than enough. Lots of powders work. SR-4759 was/is probably the best, if you can find it. Barring that, just about any fast burning powder, Red Dot, Unique, Bullseye, some use 2400 and I expect some of the newer, fast burning powders will work as well. A general rule is not to duplex more than 10% of the BP charge. Even when shooting the big 50 cal. BP Express cartridges I've never had to use more than 8% to clean up fouling and achieve the necessary velocity for double rifles to regulate.

    I never saw the need to duplex the 45-70 or any BP cartridges with a capacity of 80 grs. or less, in modern brass. My fouling difficulties always seem to start at about 90 grs. and up. Consequently, I have no 45-70 duplex loads. I do for the big 45's and a few BP Express cartridges but those are different beasts.
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  3. #3
    Boolit Master
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    I use 10 GRS. of UNIQUE or B-EYE under the black powder load, I use this load, but am not recommending it for any one else to use!

  4. #4
    Boolit Master
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    Quote Originally Posted by toot View Post
    I use 10 GRS. of UNIQUE or B-EYE under the black powder load, I use this load, but am not recommending it for any one else to use!
    hmmmm I think I would like something a bit slower than bulleye and red dot - 5 to 7 grains of 4227 works a treat

  5. #5
    Boolit Grand Master


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    You might read my posts in this thread;

    http://castboolits.gunloads.com/show...quipment/page2

    In post #36 I discuss the development of duplex loads. With 4759 not being readily available at all anymore I'm looking at substituting with 4227 or 5744.
    Larry Gibson

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  6. #6
    Boolit Master Lead pot's Avatar
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    Quote Originally Posted by toot View Post
    I use 10 GRS. of UNIQUE or B-EYE under the black powder load, I use this load, but am not recommending it for any one else to use!

    I have to ask if you really use those loads under black powder. You are in double charge loads for the .45 ACP and over loads for the .44 mag. 10 grains of bullseye has to be over 34,000 cpu with lighter bullets than used in the .45-70.

  7. #7
    Boolit Buddy Rapidrob's Avatar
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    2ND 5744. I used it for decades in my .45-70 and .40-64 rifles for long range matches.

  8. #8
    Boolit Grand Master Don McDowell's Avatar
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    In the old Ideal loading handbooks, they said no more than 10% of the powder charge should be unique powder, and NO compression.
    Duplexing really doesn't make much sense, with the plethora of suitable smokeless powders available today, and the many pressure tested sources of data.
    Long range rules, the rest drool.

  9. #9
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    Quote Originally Posted by Lead pot View Post
    I have to ask if you really use those loads under black powder. You are in double charge loads for the .45 ACP and over loads for the .44 mag. 10 grains of bullseye has to be over 34,000 cpu with lighter bullets than used in the .45-70.
    Yes, I have no idea what the pressures curve or pressure peak could be using powder like BE, but reading that post did more than raise my eyebrow a little.
    The Canadian long range BP competition rules on duplex called for no more than 20% of the total could be smokeless powder and the US NRA uses 10% as the maximum. I don't know how arbitrary the bases of these percentages are, but I would guess VERY arbitrary as it does not describe what powder or class of powders can be used.

    In the Lyman loading manual, number 45 maybe and others, there is pressure tested data for duplex loads for the 45-70 Govt. That information at least gives some clue as to what could be expected if loaded correctly. This is also supported by a link in post #5 which is worth taking the time to read if you are new to duplexing. I think you are on much safer ground going with medium and slower powders like the no longer produced SR-4759. Even IMR-3031 and Reloader-7 have been reported to work well.
    have fun -be safe.
    Last edited by Chill Wills; 01-27-2020 at 10:30 PM.
    Chill Wills

  10. #10
    Boolit Grand Master Outpost75's Avatar
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    I have found that even a small pinch of a grain or too of bulky flake smokeless such as Red Dot, Green Dot, 700X, Promo, PB in the .45-70 makes a BIG difference in reducing fouling so you can fire long strings without wiping or blow tubing.

    In a short-barrel gun not over 26 inches a .22 Short case can be used as a dip measure. If you use a dirty powder like Elephant, or have a longer barrel as in a full-length 1884 trapdoor, then a .22 LR case full will shoot cleaner and aid ignition of heavier charges using standard primers.

    I see no need to use as much as 10% of the BP charge in smokeless unless doing so necessary to reach full BP velocity in modern solid-head brass for barrel regulation.
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  11. #11
    Boolit Grand Master


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    Actually measuring the psi and looking at the time/pressure curves ("trace" to some) I find basically little difference between my M1873 duplication load using the Lee 405HB bullet over 70 gr GOEX cartridge and the duplex replicant load of 7 gr 4759/54 gr GOEX Cartridge. The PSI difference was 1,100 psi higher with the duplex load and 52 fps faster. Another lke load only using some old Dupont Superfine showed the duplex load having a 600 psi difference at 18 fps faster.

    Some, with stronger actions, use the duplex load to give higher velocity. That simply means more pressure. I don't use a duplex load for that.

    I use the duplex load in my TDs because the smokeless powder blows most of the BP residue (mostly unburned charcoal residue) out of the barrel. That means I don't have to clean the barrel, wipe it or use a blow tube at all. I do not go for more velocity but instead reduce the BP an appropriate amount of BP for each grain of smokeless used. to maintain the same velocity level as the straight BP load. That keeps the pressure fairly consistent and equal to BP loads. I explain how it is done in the thread posted in post #5. Or you can read how to make such appropriate duplex loads in Spence Wolf's excellent book on replicating original M1873 TD loads for Trapdoors. His method can easily be applied to other BP loaded cartridges.
    Larry Gibson

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  12. #12
    Boolit Master
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    Quote Originally Posted by toot View Post
    I use 10 GRS. of UNIQUE or B-EYE under the black powder load, I use this load, but am not recommending it for any one else to use!
    Yes, and I agree about the disclaimer. Good luck.

    Likely a "pinch" of BE or Unique v 10 to 20 percent is a big difference. Just as 7 grains BE under the BlackPowder, v 7 grains of SR-4759 would be as well.

    This concept is among the reasons us BPCR match competitors are seeing more and more events that are black powder only. You never know what might seem reasonable to the personal next to you and their cast Ballard.
    Last edited by Chill Wills; 01-27-2020 at 10:22 PM. Reason: typo
    Chill Wills

  13. #13
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    I can not give my source as it is locked up in my mind someplace that at the present seems unavailable.

    I learned long ago that when duplexing black powder with smokeless ... to not use the shotgun ultra fast powders. Fast rifle powders seem to work well without producing serious pressure lurch's.

    Also to produce safe loads ... decrease the black powder 3 to 1 grains ... in other words ... for every grain of smokeless powder, decrease the black powder by 3 grains.

    Example;

    Take the 45-70 case. 70 grains powder duplexed is such ... 3 grains of IMR 4227 under the reduced black powder charge of 61 grains.

    This is my favorite duplex load by the way ... 3 grains of IMR 4227 in the case first. Follow with 61 grains of dirty GOEX 2F black powder. This load is dandy under Lee's 405 grain hollow base boolit and this lubed with SPG bullet lube. Sparked up with either Remington 9.5 large rifle primers or CCI regular large rifle primers. Crimp over the first drive band. These do real well in every 45-70 I have tried it in.

    My reason for duplexing blackpowder was when shooting in Alaska in winter time in -30 degree and colder weather when a spit patch will freeze to the barrel when trying to swab out the BP fouling. Shooting these duplex's keep a surprisingly clean barrel while shooting the pleasant smelling and very fun black powder.

    This suggestion and example is just worth what you paid for it ... loaders beware and go at your own risk as these loads are not proven safe in a clinical setting.
    WHEN ALL IS SAID AND DONE...MORE WILL BE SAID THEN DONE

  14. #14
    Boolit Master
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    I just wanted to use black powder and don't want the fouling problems.

    Which black powder do I need to buy?
    " If you cant do it with a 308 , you dont need to do it!

  15. #15
    Boolit Grand Master Don McDowell's Avatar
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    Olde Eynsford or Swiss 2f, but just as important if not more so as the powder is using a good lube.
    Long range rules, the rest drool.

  16. #16
    Boolit Master
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    Quote Originally Posted by Chill Wills View Post
    Yes, I have no idea what the pressures curve or pressure peak could be using powder like BE, but reading that post did more than raise my eyebrow a little.
    The Canadian long range BP competition rules on duplex called for no more than 20% of the total could be smokeless powder and the US NRA uses 10% as the maximum. I don't know how arbitrary the bases of these percentages are, but I would guess VERY arbitrary as it does not describe what powder or class of powders can be used.

    In the Lyman loading manual, number 45 maybe and others, there is pressure tested data for duplex loads for the 45-70 Govt. That information at least gives some clue as to what could be expected if loaded correctly. This is also supported by a link in post #5 which is worth taking the time to read if you are new to duplexing. I think you are on much safer ground going with medium and slower powders like the no longer produced SR-4759. Even IMR-3031 and Reloader-7 have been reported to work well.
    have fun -be safe.
    Chill, I didn't shoot black powder long range up here ( I'm Canadian ) when everyone was shooting hot rod duplex loads, but most of the old guns I know of were rebarreled Ruger #1's which can survive higher pressures than your average antique. I never heard of anyone using Unique though. Usually SR-4759, Hercules Reloder 7, or 4227.

    Chris.

  17. #17
    Boolit Master
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    Yup, 10% 4227, 90% real black powder, no compression, no airspace.

  18. #18
    Boolit Master
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    Quote Originally Posted by Chill Wills View Post
    Yes, I have no idea what the pressures curve or pressure peak could be using powder like BE, but reading that post did more than raise my eyebrow a little.
    The Canadian long range BP competition rules on duplex called for no more than 20% of the total could be smokeless powder and the US NRA uses 10% as the maximum. I don't know how arbitrary the bases of these percentages are, but I would guess VERY arbitrary as it does not describe what powder or class of powders can be used.

    In the Lyman loading manual, number 45 maybe and others, there is pressure tested data for duplex loads for the 45-70 Govt. That information at least gives some clue as to what could be expected if loaded correctly. This is also supported by a link in post #5 which is worth taking the time to read if you are new to duplexing. I think you are on much safer ground going with medium and slower powders like the no longer produced SR-4759. Even IMR-3031 and Reloader-7 have been reported to work well.
    have fun -be safe.
    Chill
    I agree 100% with you and Lead Pot -------10 grains of bullseye or red dot ?? no thank you very much !!!! ( I have a stack of fast shotgun powder I inherited and looking for a use for it too - but not going in any of my big rifle cases)

  19. #19
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    Quote Originally Posted by Gunlaker View Post
    Chill, I didn't shoot black powder long range up here ( I'm Canadian ) when everyone was shooting hot rod duplex loads, but most of the old guns I know of were rebarreled Ruger #1's which can survive higher pressures than your average antique. I never heard of anyone using Unique though. Usually SR-4759, Hercules Reloder 7, or 4227.

    Chris.
    I always wondered why they ever let Duplex loading into long range competitions ----until I did some testing - I can get better ES numbers with straight black than I can do with duplex - so I figure the blokes at the top end of the competitions already knew that ?

  20. #20
    Boolit Master
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    Joe I got into it after the duplex loading phase of BP competition shooting was more or less over. I've heard that with lower quality powder like plain Goex, you can get better velocity stats, and more velocity by going to duplex loads. I have shot a few duplex loads when experimenting over the years but have never shot any over a chronograph. I'm very happy using straight Swiss, and occasionally OE.

    Chris.

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