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Thread: Duplex loads

  1. #1
    Boolit Buddy
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    Duplex loads

    Anyone use them?

    Been my favorite for large capacity cases for a fair spell.

  2. #2
    Boolit Buddy
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    I think duplexing is a rule violation to use duplex BP+smokeless in shooting games competition.

    I’m not a competitor in any shooting game competition but was thinking of trying 45 Colt with 2 grains of middle burn rate smokeless Hodgdon’s CFE-Pistol added and remove 6 to 8 grains of the BP from my usual amount of straight 2fg 35 to 36 grains of GOEX that I load.

    I just shot off the last of my GOEX. I haven’t got enough experience with the 2fg Old Eynsford that I purchased to replace the GOEX to is see if the better quality Old Eynsford would benefit from being duplexed.
    The small amount of use I have with OE make me think it might not be worth the extra aggravation of building duplexes loads at least not for use in revolvers.

    Rifle usage might be totally different, if the duplex loads could hold great or greater accuracy without the need for barrel wiping every 10 to 15 shots I would definitely add duplexing as my normal BP hand-loading routine.
    Last edited by greenjoytj; 04-07-2021 at 11:16 AM. Reason: Spelling & grammar

  3. #3
    Boolit Master
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    There’s a sort of “Laffer Curve” of shooting vs. cleaning with black powder and caliber.

    With normal powder charges, I do more shooting than cleaning/fouling management down to .38 caliber. With a powder charge of 50 or so grains, I still spend more time shooting than cleaning.

    Below .38 caliber, I do much more cleaning than shooting with straight black, so duplexing comes in here. Generally 4 or 5 grains of 4759 (the best smokeless for duplexing I’ve found) with a properly reduced charge of black in .32-35s, .32-40s allows shooting with no cleaning at all until the session is done. I’ve also duplexed a bit with the .40-90-3-1/4” shell. The freakishly heavy powder charge needs more cleaning than other cartridges of this caliber, but not as much as the smaller bores. .25-21s and .25-25s also benefit from duplexing, with a smaller smokeless charge, of course.

    With most .38 and larger bores, duplexing can be done, but the velocity variations induced may compromise the accuracy. In those cases, I’d rather do the nominal amount of cleaning, wiping, blowtubing or whatever, necessary than mess with duplexing.

    One does have to check the powder levels twice, once with a flashlight to check the smokeless level and a final check on the black level before compression, but it takes less time than the cleaning between shots, for sure.

  4. #4
    Boolit Buddy
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    I’ve used 4759 and 4227. Prefer the former. 10% of charge weight is the “booster” and the balance in BP which winds up mildly compressed. Cartridges I’ve toyed with include .25-20 SS, .38-55 and .45-70. In all cases less cleaning, and better accuracy. Probably my best day was 5 in 1.5” at 100 yds with the .45-70 and elbow rest.

  5. #5
    Boolit Bub
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    greenjoytj,

    Of much greater importance in the 45 Colt is having adequate black powder lubricant on your bullet. Since I started loading Big Lube bullets (250g RNFP) I have routinely fired 25 rounds without needing to clean. On one occasion I fired 90 rounds through two 45 Colt single action revolvers, and neither gun required cleaning to keep functioning or to hit what I was shooting at.

    I am not a fan of duplex loads for rifles and particularly not for handgun cartridges. And you will find Olde Eynsford a superior powder to GOEX, despite being made by the same folks. Think of OE as the premium brand.

    Dave

  6. #6
    Boolit Master
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    I've done it with .357 magnum and 45-70. It work but the loading process was tedious. In my opinion it just wasn't worth it, especially for small batches.
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  7. #7
    Boolit Buddy
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    Quote Originally Posted by Dave T View Post
    greenjoytj,

    Of much greater importance in the 45 Colt is having adequate black powder lubricant on your bullet. Since I started loading Big Lube bullets (250g RNFP) I have routinely fired 25 rounds without needing to clean. On one occasion I fired 90 rounds through two 45 Colt single action revolvers, and neither gun required cleaning to keep functioning or to hit what I was shooting at.

    I am not a fan of duplex loads for rifles and particularly not for handgun cartridges. And you will find Olde Eynsford a superior powder to GOEX, despite being made by the same folks. Think of OE as the premium brand.

    Dave
    Too bad the Big Lube 250 gr bullet drops at .456” instead of a more modern .452” dia.

    I have a 255gr SAECO #955 RNFP with a good size lube groove that drops at .456” after sizing to .452” the crimp groove is virtually smeared shut from displaced lead.

    I’ve read the pre WW2 Colts have large bores that require bigger diameter bullets, but post WW2 barrel are .451” which use the .452” dia cast bullets.
    I would think mold makers would cut their mold diameter for the modern 45 Colt bore size as the market for molds is with the new guns.

  8. #8
    Boolit Master
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    Yes, I have one rifle for which I duplex all loads but, for a different reason than most duplex. To date no straight black powder, of any brand to include Swiss or OE, has produced enough velocity for my Goldmann double rifle to regulate, with any weight bullet, after 25 years of ownership and working with the rifle. The very best load to date has been 5 grs. of SR-4759 under 70 grs. of the old GOEX Cartridge....of which I'm down to my last pound so new load development is in the future. I worked toward the least amount of smokeless necessary to achieve the required velocity.

    The load shoots vey clean, as any who have used duplex loads know. It's sub 3 inch accurate, composite group, at 75 yards, open sights, which isn't bad for a 130+ year old rifle with slightly pitted bores....and 68 year old eyes.

    Other than the above, I've only played with duplex loads in a couple big bores, 45-100 and 45-120. They did shoot clean and obviously the need for fouling control was significantly reduced....and honestly, accuracy was better.
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  9. #9
    Boolit Master



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    I don’t see the point. Why not just shoot smokeless, if you don’t want to deal with fouling. However, when I am shooting BP in my 45/70, I often shoot a smokeless round or two at the end and it makes cleaning a lot easier.

  10. #10
    Boolit Buddy
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    Well, one reason would be some guns are not suitable for smokeless loads. It's called damascus steel.



    Another is that some want a load that permits repeatable shots w/o degradation in accuracy. Is useful for some hunting scenarios. Maybe another reason is that some just want to play with it. The target below was shot offhand at 100 yards w/o bore wiping or blow tubes.


  11. #11
    Boolit Grand Master Nobade's Avatar
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    Also because some rifles perform much better with duplexed black powder ammo than they do with straight smokeless, especially at the same pressure levels. I have quite a few that fall into that category, including a Marlin 44 mag, a Swiss Vetterli, an Argentine rolling block, a H&R 38-55, a Trapdoor, and others. None of those rifles can produce comparable accuracy using straight smokeless powder.

  12. #12
    Boolit Master
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    For me the first foray into duplex loads had nothing to do with fouling. It was to achieve the required velocity at acceptable pressure so two barrels from a double rifle would shoot together. As mentioned, it was for a 130+ year old rifle on a Lefaucheux action that isn't known for its strength. That's the point. I wish I could have gotten it regulated with straight black but it didn't happen and unless someone comes out with a new Curtis & Harvey #6, it isn't likely to happen.

    Trail Boss and 5744 are both next to useless in a double. I tried both when they came out, in two different BP proofed doubles. The Goldmann and an E.M. Reilly in 500 BPE. They will not generate enough velocity at an acceptable pressure and groups were often simply wild. 5744 MIGHT work in some doubles but not all. No one I know who has tried Trail Boss in a double has come close to regulation. It's just too slow.
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  13. #13
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    I do not shoot competition with BP so the "rule" prohibiting duplex loads mean nothing. If I'm going to shoot BP in my trapdoors, and I do frequently, I use duplex loads which replicate the 45-70-405, 45-70-500 and the 45-55-405 service loads. I use 4759 under GOEX cartridge or FFFg BP.

    The reasons are several. Clean up of the rifle per se at the end of shooting isn't much different than with straight BP loads. However, during shooting, the need to maintain accuracy with straight BP loads requires wiping the fouling out of the bore every so many rounds. Doing so while shooting at the bench or even during a match poses not real problem. However, on my walk abouts in the desert of mountains I find carrying the necessary rod, patches and cleaners isn't practical. Neither is it practical when I find myself pinned down by "hostiles to the front" [rocks, stick, cowpies, pine cones, etc. please allow me amy hallucinations....] I can shoot my way out without any loss of accuracy or need of bore cleaning. With the duplex loads I do not have to wipe at all because the fouling [unburnt charcoal residue mostly] is blown out of the barrel with each shot. I have fired over 100 shots of 45-70-505 and 45-55-405 in my Officer's Model and carbine M1973s w/o wiping or cleaning and accuracy was as good at the end as at the beginning. Speaking of accuracy I also find the duplex load to be every bit as accurate as straight BP or smokeless loads. The cases also clean up easier with the duplex loads as there is no, or at least little, BP fouling inside the cases.
    Last edited by Larry Gibson; 04-08-2021 at 10:53 AM.
    Larry Gibson

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  14. #14
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    Larry , thank you for your post . I have an old Winchester 94 in 38-55 that left the factory in April 1897 , according to records . I have seriously contemplated going bp using a duplex load . I will need a bigger lube bullet . Your post put my concerns to rest . Regards Paul

  15. #15
    Boolit Grand Master


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    I use Spence Wolfe's method of developing the duplex 45/70 loads and have used it the same with other cartridges. The intent was not to increase velocity or "power" but to blow the fouling out of the barrel so wiping isn't necessary. Pressure testing has proven the increase in psi is minimal if any. My duplex service load replicants are still less than the SAAMI MAP for the 45/70 intended for TD level loads.

    FYI; They say the West was "won" by the '73 Winchester. Truth be told, the West was made safe by the Army with 45/70 TDs so the cowboys could "win it" with the '73s Winchesters.....

    Photo is of the some of the guns mentioned which were used in a test of VV Tin Star in numerous cartridges for SASS cowboy action shooting.

    Click image for larger version. 

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    Larry Gibson

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  16. #16
    Boolit Master
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    Larry, you mention the pressure of duplex loads. Kynoch and Birmingham Proof House tested several double rifle, duplex loads provided by Grahame Wright. I was surprised that more than a few actually tested lower pressure than the original, straight black powder loads. As with several things firearm and reloading related, what was once thought to be fact melts away in the light of fact.
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  17. #17
    Boolit Master
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    Quote Originally Posted by Goofy View Post
    I’ve used 4759 and 4227. Prefer the former. 10% of charge weight is the “booster” and the balance in BP which winds up mildly compressed. Cartridges I’ve toyed with include .25-20 SS, .38-55 and .45-70. In all cases less cleaning, and better accuracy. Probably my best day was 5 in 1.5” at 100 yds with the .45-70 and elbow rest.
    I tried both these and did better with 4227 --the SR 4759 I had was likely 40 years old may have been part of the reason for that.

  18. #18
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    Quote Originally Posted by sharps4590 View Post
    Larry, you mention the pressure of duplex loads. Kynoch and Birmingham Proof House tested several double rifle, duplex loads provided by Grahame Wright. I was surprised that more than a few actually tested lower pressure than the original, straight black powder loads. As with several things firearm and reloading related, what was once thought to be fact melts away in the light of fact.
    I have found that also, not always but enough to know the 1st time was not an anomaly. I surmise the reason being is, with the duplexing technique of Spence's that I use, the charge of BP is proportionally reduced to the charge of smokeless powder used. Many erroneously think duplexing is just adding additional smokeless to the BP charge. Doing that, in fact, does increase pressure. The way Spence recommends duplexing is to lesson the BP charge proportionally to the smokeless powder charge which sort of evens the pressure out.
    Larry Gibson

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  19. #19
    Boolit Buddy
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    Larry, thanks for your comments, very good information.

  20. #20
    Boolit Master
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    Quote Originally Posted by Larry Gibson View Post
    I have found that also, not always but enough to know the 1st time was not an anomaly. I surmise the reason being is, with the duplexing technique of Spence's that I use, the charge of BP is proportionally reduced to the charge of smokeless powder used. Many erroneously think duplexing is just adding additional smokeless to the BP charge. Doing that, in fact, does increase pressure. The way Spence recommends duplexing is to lesson the BP charge proportionally to the smokeless powder charge which sort of evens the pressure out.
    Interesting
    I have kept duplexing to the stronger action guns, model 92 and 86 - experience is a gain of about 100FPS velocity - I have a chronograph but no way of testing pressure and approached this from the "no free lunch" angle

    loads are full case with normal blackpowder compression - I use a LEE scoop measure, 0.5cc gives me 7 grains of 4227 - (4227 has identical density to my blackpowder so its a one for one exchange) its really a simple process to dump a scoop of 4227 down then add the black charge. Chrono test on the 86 gave me single digit ES for a string of ten shots (can get that with straight black too)

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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"
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GC Gas Check