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Thread: Duplex loading for 45/70

  1. #1

    Duplex loading for 45/70

    I have seen a couple posts talking about duplex loads, small amount of pistol powder in under full case of black. Would anybody expand on that.

  2. #2
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    JonB_in_Glencoe's Avatar
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    It sounds dangerous to me. I wouldn't do it, it seems like it wouldn't be necessary, unless you have a batch of homemade BP that's tough to ignite? ...but anyway, I guess if you have a hanker'n for experimenting, someone out there may have some experience doing it, since it's been listed in a published reloading manual.

    I was the person who mentioned seeing it in a old Lyman manual
    http://castboolits.gunloads.com/show...=1#post4471218

  3. #3
    Boolit Master



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    In the early 1900's it was very common for competition shooting. It greatly reduces fouling. Most BP competitions do not allow it today.

    http://castboolits.gunloads.com/show...r-duplex-loads

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    I don't use pistol powder for duplexing. I start with a pretty slow powder, 5 gr. or thereabout and see how fouling and accuracy is. Go to slightly faster powder until one gives desired results. Pretty common in BPCR competition.
    For smokeless powder, I use a kicker with a full case of WC860, staying right around 1170 fps, to try to remain under the sonic transition speed.
    The solid soft lead bullet is undoubtably the best and most satisfactory expanding bullet that has ever been designed. It invariably mushrooms perfectly, and never breaks up. With the metal base that is essential for velocities of 2000 f.s. and upwards to protect the naked base, these metal-based soft lead bullets are splendid.
    John Taylor - "African Rifles and Cartridges"

    Forget everything you know about loading jacketed bullets. This is a whole new ball game!


  5. #5
    In Paul Matthews book "Forty years with the 45-70" he talks about smokeless duplexing quite
    a bit. Might want to check out his book, it is a good one.
    The insulated state in which nature has placed the American continent should so far avail it that no spark of war kindled in the other quarters of the globe should be wafted across the wide oceans which separate us from them." -- Thomas Jefferson

  6. #6
    Boolit Master
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    Quote Originally Posted by waksupi View Post
    For smokeless powder, I use a kicker with a full case of WC860, staying right around 1170 fps, to try to remain under the sonic transition speed.
    This has been the extent of my "duplex loading"--1 grain of IMR-4198 in the kicker per 8 grains of WC-860 as main charge, with about 1/10" compression to keep things located in the charge chamber. I have not tried this in any Trapdoors, just a couple Marlin 95s and a Ruger #1. This practice burns up the bore trash that unassisted/weakly-assisted WC-860 leaves behind in the 45/70, and as Ric states a 405 grain cast bullet stays under 1200 FPS. Using the Lee 405 grain plain-base casting, 5-shot groups of 1-1/8" to 1-1/4" at 100 yards were routine from the #1 and its NEGC aperture sight.

    Lyman #462560 (552 grain Mastodon Flattener, a flatnose gas-check design meant for the 458 Win Mag) gets about 1100 FPS in the Ruger #1, and in that 7-1/4" rifle the recoil on one end is about the same as on the other. These were not really accurate, the bullet length was not a good match to the slow twist (1-20"). 458 W/M get a 1-14" twist in most rifles.
    I don't paint bullets. I like Black Rifle Coffee. Sacred cows are always fair game. California is to the United States what Syria is to Russia and North Korea is to China/South Korea/Japan--a Hermit Kingdom detached from the real world and led by delusional maniacs, an economic and social basket case sustained by "foreign" aid so as to not lose military bases.

  7. #7
    Boolit Buddy
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    Quote Originally Posted by pressonregardless View Post
    In Paul Matthews book "Forty years with the 45-70" he talks about smokeless duplexing quite
    a bit. Might want to check out his book, it is a good one.
    I couldn’t find the book on Amazon. Does anyone know where it is available?

    Thanks

    Edit: I just found it on Amazon searching the author’s name and adding middle initial A.
    Last edited by GregLaROCHE; 10-09-2018 at 05:14 PM.

  8. #8
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    3 to 5 grains of SR4759 and 60 grains of "lightly compressed" Goex FFg black powder and either the 405 or 500 grain lead bullet is the duplex load that was offered on the old Lyman loading books from the 50s. I have used this quite successfully in my Springfield M88 Trapdoor rifle and other .45-70. It is an accurate, and very clean-burning load that eliminates the necessity of blow-tubes or lube cookies. I have done the same thing substituting WC860 smokeless powder with similar results (but no need to wash cartridge cases) I had had even better results with duplexed WC860 in the 6.5X55 Swedish Mauser with 140 grain bullets. Duplexing totally eliminated unburned powder being left in the bore using this very slow powder.

  9. #9
    Quote Originally Posted by GregLaROCHE View Post
    I couldn’t find the book on Amazon. Does anyone know where it is available?

    Thanks
    Check some of these listings -

    https://www.amazon.com/gp/offer-list...n=new&qid=&sr=
    The insulated state in which nature has placed the American continent should so far avail it that no spark of war kindled in the other quarters of the globe should be wafted across the wide oceans which separate us from them." -- Thomas Jefferson

  10. #10
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    5 grains of SR 4759 was the preferred kicker for many who duplexed 45-70. As 4759 is no longer manufactured, 4227 is about as close as one can get now.

    While duplexing has been done since before WW II, much study should be done and consulting with those who have direct experience, before trying it yourself.
    Last edited by smokeywolf; 10-09-2018 at 05:35 PM.
    A well regulated militia, being necessary to the security of a free State, the right of the People to keep and bear arms *shall not be infringed*.

    "The greatest danger to American freedom is a government that ignores the Constitution."
    - Thomas Jefferson

    "While the people have property, arms in their hands, and only a spark of noble spirit, the most corrupt Congress must be mad to form any project of tyranny."
    - Rev. Nicholas Collin, Fayetteville Gazette (N.C.), October 12, 1789

  11. #11
    Boolit Buddy
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    I’ve been itching to load some black powder for my .45-70 Marlin. Everyone says “Don’t do it. It will make a real mess in a lever gun.” Could a duplex round help solve this problem?

  12. #12
    Boolit Master
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    Quote Originally Posted by GregLaROCHE View Post
    I’ve been itching to load some black powder for my .45-70 Marlin. Everyone says “Don’t do it. It will make a real mess in a lever gun.” Could a duplex round help solve this problem?
    It can. I did it in my 1894 (.357) just to test Matthews' method. I figured I could find out if it worked and would burn a lot less powder than my 45-70.
    The load data was developed using his formula, in this case 21.0 gains of 3F over 2.0 grains of SR4759, 158grain LSW.
    Warning: I know Judo. If you force me to prove it I'll shoot you.

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    I have to comment on the Matthew's book. I got it, read it, and re-sold it, something I seldom do with a load book. I didn't see much I didn't know, and there is much more information on the .45-70 on this forum than is in the book.
    The solid soft lead bullet is undoubtably the best and most satisfactory expanding bullet that has ever been designed. It invariably mushrooms perfectly, and never breaks up. With the metal base that is essential for velocities of 2000 f.s. and upwards to protect the naked base, these metal-based soft lead bullets are splendid.
    John Taylor - "African Rifles and Cartridges"

    Forget everything you know about loading jacketed bullets. This is a whole new ball game!


  14. #14
    Boolit Master fredj338's Avatar
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    Back in the day of few powder choices, this was viable for the handloader looking for improved performance. Today, just do not see the point. Pick a powder that meets your vel needs & just load that. It's not worth the potential accident of too much fast burning pistol powder.
    EVERY GOOD SHOOTER NEEDS TO BE A HANDLOADER.
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  15. #15
    Boolit Master fredj338's Avatar
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    Quote Originally Posted by GregLaROCHE View Post
    I’ve been itching to load some black powder for my .45-70 Marlin. Everyone says “Don’t do it. It will make a real mess in a lever gun.” Could a duplex round help solve this problem?
    No. BP just leaves a crud in the barrel & film on everything else. There is a reason smokeless powder was invented & why BP is still not loaded much but for the enthusiast. When I did BP in a Sharps, I just loaded mag primers, loads were fine, but it is still a mess to clean up.
    EVERY GOOD SHOOTER NEEDS TO BE A HANDLOADER.
    NRA Cert. Inst. Met. Reloading & Basic Pistol

  16. #16
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    I think everybody has this one backwards. In the 16" guns on a battle ship they used a pack of black powder to ignite the packs of smokeless powder that was much slower burning. So black powder was the "kicker" here. In the 45-70 a small load of smokeless pistol powder was used behind the black powder to keep the barrel much cleaner and avoid having to swab the barrel between shots. Not a "kicker" to get the black powder burning. I have experimented with using a fast pistol powder in rifle cases to get a 50 BMG slow powder burning in them and to just try to use up the several jugs of 50 BMG powers I have. It just wasn't very effective and I just went back to more "normal" powders (4985, 4198, 4759 etc.) for both target shooting and deer hunting.

  17. #17
    Boolit Master
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    A 10% charge of 4759 or 4227 under a full case of BP is safe and much cleaner burning, much better for hunting or field shooting as you don't need to blowtube or swab to get the next cartridge chambered. It is generally not legal in competition and I find that it kicks a bit more, prolly because of a more complete burn.

  18. #18
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    From my treatise on my 45-70 trapdoor loads;

    PART III:

    I had several reasons for developing duplex 45-70 loads. Maintaining accuracy w/o cleaning between shots or every 10 shots or so was foremost as I didn’t want to carry a lot of cleaning equipment with me on “walk about” shoots where upwards of 50 shots would/could be taken. I also really detested the use of the blow tube between shots. Increasing the “power” of the loads was not a consideration at all. I wanted simply to lessen the fouling while maintaining original ballistics within the psi range safe for TDs and perhaps improving upon accuracy.

    The smokeless powder charge against the primer aides in ignition alleviating the need for drilling the flash holes and other makes of cases with thicker walls can also be used. The smokeless charge, if sufficient, also “blows out” of the barrel most of the charcoal residue from the BP. This can be seen easily seen by looking from the breach end down the bore after several regular BP rounds have been fired. This residue (BP fouling) builds up and not only destroys accuracy but also can prevent the chambering of a bullet with a tight bore riding nose. The blow tube softens the residue in the leade allowing the bullet to be seated. However, after sufficient rounds fired w/o swabbing or cleaning and chambering, even with the use of the blow tube, will be difficult. [Note; this is why a true M1873 bullet is not a bore rider and the M1882 bullet’s nose is smaller than the bore in diameter sp both will still chamber even after many rounds have been fired] With an efficient smokeless ignition charge there is little charcoal fouling left in the leade and bore so the use of a blow tube to “keep it soft” is no longer needed.

    Additionally with most of the charcoal residue blown out I have found accuracy of a 405 gr bullet that fits the groove diameter and not depending on obturation to fit the bore will not quite but almost as accurate to 800 yards as the M1882 500 gr bullet.

    In developing my own duplex loads I followed Spence’s advice and use IMR 4759 (SR4759) as the smokeless powder in my duplex loads. I had picked up a hundred once fired R-P nickeled cases to use as they would, if useable, allow a quick identification of the duplex load vs a smokeless of straight BP load. Those cases would chamber in my TD so they were close to “fire formed”. I cleaned and NS’d them. I used standard WLP primers and did not drill the flash holes. Actually nothing other than cleaning and inspecting was done to the cases. I started off using 5 shot test strings with 4 gr of 4759 against the primer and (using Spence’s bulk formula of 1 gr 4759 = 2.8 gr FFG) reduced the amount of GC (GOEX Cartridge) by 11gr to 59 gr. Care bust be taken that the seated bullet still compresses the total powder charge. I have not found the compression die to be needed with the 500 gr bullet and probably is not needed with the 405 gr bullet But I use it anyway. I compress the powder so the bullet, at a cartridge AOL of 2.55” for the Lee 405HB, just sets on top of the powder. I use the taper crimp die to just put a slight taper crimp on the case mouth. Additional test loads to, increasing the 4759 1 gr per test while decreasing the GC approximately 2.8 gr per test, 7 gr 4759 and 50 gr GC were loaded.

    Shooting the 5 shots in each test load and inspecting the bore showed that 7 gr of 4759 did indeed “blow out” most all of the charcoal (black streaks) residue and fouling. The barrel was cleaned between test strings. I also found that accuracy steadily increased as the 4759 was increased. Velocity was lower than the 1340 - 1350 fps I was looking for to duplicate M1873 service ballistics. I then kept the smokeless load at 7 gr and began increasing the GC in 1 gr increments. I found that with 7 gr 4759 under 52 gr GC in the fire formed R_P nickeled cases with the 16-1 Lee 405HB the velocity was right at 1340 - 1350 fps, just where it should be to match original ballistics out of the 32 ˝” original TD rifle barrel. I have subsequently pressure tested that load (Oehler M43) and found the psi to be 20,300 psi(M43), well within the psi MAP of 28,000 for the TD. The ten shot psi test had an SD of 10 fps and an ES of 30 fps.

    That has been my standard M1873 BP duplex load for use in my H&R Officer’s Model. I have a M1879 “R” Type III (3rd form) rear sight on it and a Beech front sight along with the factory tang sight. With the rear sight set at 100 yards and using the blade of the Beech front sight the POI is just above POA at 100 yards. I generally can hold 10 shots into 2 – 3 moa with the M1879 rear sight (I do better with the tang sight of course). The range regulations have proven quite correct to 1000 yards.

    I next wanted a 45-55 carbine load with the 405HB at 1150 fps out of my H&R LBH Carbine. I took the tang off the LBH (why it was put there is beyond me!) and installed a “C” M1879 Type IV (4th form) rear sight with a blade front sight. I dropped the 4759 charge back to 5 gr (thinking it shouldn’t take as much smokeless to blow the BP residue/fouling out of the shorter 22” carbine barrel proved correct) and loaded 42 gr GC over it. Care must really be used to make sure the bullet does slightly compress the powder. The 405HB had to be seated under 2.55” OAL for some slight compression just as the original 45-55 w/o a wad in it. I left the 4759 charge at 5 gr and increased the GC until 49 gr gave 1138 fps at 15’ with an SD of 6 and an ES of 18. These were loaded with the 405HB cast of 16-1 and sized .4615 and lubed with my beeswax/olive oil lube. I have since switched to the 457124 Lyman cast of the same alloy. It gives almost identical ballistics and is easily identifiable as the 45-55 load by the different bullet.

    These duplex loads have met my every expectation. They are accurate, I do not use a blow tube any longer and I can literally shoot all day w/o losing accuracy from hardened or excessive BP fouling. During a test one time there was 80+ rounds fired from the H&R OM and 100+ from the H&R Carbine in one day w/o cleaning, blowing or anything else. At the end of the test I fired a 5 shot group from each at 100 yards and found they both still were as accurate as if clean. Speaking of cleaning; it is also so much easier w/o all the BP charcoal residue.

    Ok, so what about my original TD target rifle? Well, that was supper easy; I used the same load as for the M1873 405HB bullet and simply substituted the M1882 500 gr bullet cast of 16-1 form the Rapine 460500 mould. Those bullets drop exactly at 500 gr BTW and were sized at 4615 and also lubed with my beeswax/olive oil lube. This time I used standard R-P cases that were fire formed and NK sized. Primers were again WLRs (Other standard and magnum primers have been tested with little or discernable use with these duplex loads). The .4585 expander was used. Both the charges (4759 and 52 gr GC) were thrown with a Lyman 55 and no drop tube used). The compression die was used. Seating was adjusted so the front 1/3 of the driving band was engraved by the leade when the breach block was shut. The taper crimp die is used to just straighten out the case mouth bell. I fired 2 foulers and then 10 shots for record at 200 yards. The group was 2.9”, the velocity was 1200 fps with an SD of 4 and an ES of 14 fps. What could I say except ….sweet!
    Larry Gibson

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

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  20. #20
    Boolit Buddy
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    DonMountain,distinctly remember a video clip of the sequence of loading the powder bags on a 16" naval gun. In one of them you can see what looks like a white patch about 6"x6" being slapped on the back of one of the powder bags. Been so long since I've seen it and you jogged my memory. Frank

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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