Duplex loads

Discussion in 'The Ammo & Reloading Forum' started by reynolds357, Dec 17, 2011.

  1. reynolds357

    reynolds357 Former Guest

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    I know they are unsafe, but just out of curiosity has anyone ever developed any duplex loads? They have always fascinated me, but I have never been brave enough to cook any up with powders of vastly different burning rates. I have duplexed slow and medium slows but never slow with fast. Anyone done it? I have a friend who has done it for many years, but he is so darn secretive I cant get any useful info. out of him.
  2. jack404

    jack404 Former Guest

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    there was some field trailed and a batch left was put on the market but that's all i heard or read
  3. jack404

    jack404 Former Guest

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  4. reynolds357

    reynolds357 Former Guest

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    Are we talking about the same thing? I am talking about reloading a case with two different burning rate powders. The fast powder goes on top of the slow powder in a compressed load. The fast powder gets lit last and you get hyper velocity if you do it right and a blown up rifle if you do it wrong.
  5. jack404

    jack404 Former Guest

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    no sorry i'm thinking two projectiles only,, not powders
  6. Popgunner

    Popgunner New Member

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    Hornady 's leverevolution factory loads are duplex loads & they get velocities that are higher than we can match. Hornady is not letting slip info about what powders they use or how they do it.
  7. JLA

    JLA Well-Known Member

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    You might pick hubel458's brain on this one. I know he duplexes his wildcat 12FH loads with about 15-20 grains of bluedot as an igniter charge under a full case of a slow rifle powder.

    I dont have the balls to mess with duplex charges. IMO theres no need if all you load is normal centerfire ammo.
  8. RandyP

    RandyP Member

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    I have three friends who like to experiment - Stumpy, Lefty and Blind Joe. Want their numbers? lol

    On a serious note, there are so many great powders out there for all applications for us non-commercial reloaders, why take on tremendous isk without need?
  9. reynolds357

    reynolds357 Former Guest

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    I have never heard of fast being used under slow except for Elmer Keith using fast behind slow on the OKH cartridges that had the front ignition tubes. In essence, in that case fast behind slow is the same as fast on top of slow in a normal case. That is interesting. Maybe hubel will weigh in on this one.
  10. reynolds357

    reynolds357 Former Guest

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    You are not blending to come up with a better powder. What you are doing is moving the bullet just a bit down the barrel before the fast burning powder gets lit. It is my understanding, and anyone feel free to correct me if I am wrong, that maximum pressure develops very shortly after the charge is lit and progressively goes down from that point. The concept behind duplexing is to make the pressure go up instead of down.
  11. RandyP

    RandyP Member

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    Again it ain't MY fingers and eyes so my interest is purely conversational.

    There are powders out there to create most any velocity for most any bullet with tested published safe load data. The concept behind duplexing to 'me' is to see how far off safe a person can get before losing body parts...and for 'me' that is plain stoopid.

    It is the very nature of the human condition that here will always be a few folks who will always prove Mr Darwin and Mrs Gump correct in their counsel.
  12. reynolds357

    reynolds357 Former Guest

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    It cold be totally false, but from what I was told the concept was developed in battleship guns. They had always used a very small charge of fast powder behind the slow powder because it was so hard to light. To extend the range, they found that reducing the charge of slow burning powder and adding faster powders in its place on top of the charge of slow powder accomplished this. This is what I was told by a veteran of a battleship. He said they had three different colored charge bags that comprised a load. A small bag of a very fast ignitor powder, several bags of extremely slow powder, then a couple bags of fast powder.
  13. RandyP

    RandyP Member

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    Yes, but a 16" gun off the Missouri is a royal PIA to carry concealed.
  14. DidI

    DidI New Member

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    I got it . . I GOT IT.... braallie triggers. and they will say.... : NEVER and I mean NEVER use strange powder combinations. Can we get all that on a smaller sliver of steel?
    BUT to each his own. But I want to live to shoot another day.
  15. Bindernut

    Bindernut Well-Known Member

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    To get consistent results with duplex/triplex loads you MUST load at 100% load density or above (compressed), otherwise as the cartridges are carried around the powder charges will mix together and you'll lose the advantage that you're trying to achieve and your pressure results will be erratic. If you're duplexing up on the top-end of the pressure scale, can you say BOOM?
    Me? I don't. I do know a few older guys that were around back when that was acceptable wildcatting practice though.

    What Hubel is doing with that 12FH is using the BlueDot as a starter for slow burning rifle powder. Some blackpowder cartridge shooters are doing the same thing with the large BP cartridges. Using a small charge of a fast-burner to ignite a big main charge.
    With the 12FH We're talking like a .75 caliber cartridge here though too...darn near a small field artillery piece!
    It's the same concept as using a fast ignitor charge in the loose-bag naval guns (16" US, 38cm SK C/34, etc) The British 13.5" and 15" navals used a similar fast starter charge except as part of the initial cordite charge bag.


    There's lots of info on hubel458's 12FH ongoing saga in this thread. He doesn't pop in to often except to update that thread. You don't see him around the rest of the board much either. It's an interesting read.
    http://www.thefirearmsforum.com/showthread.php?t=27656


    I know a couple guys here that futzed around with some of the Gibbs front-ignition wildcats (similar system as the OKH front-ignition setup). They pretty much settled on not bothering with the front-ignition and just formed their cases as traditional rear-ignition cases instead.
    Back then, with very few powder choices to pick from some guys tried all sorts of interesting (dangerous) things to squeeze more fps out of a cartridge. With the advent of better pressure measuring and other load development methods, it is generally wiser to find a larger case and stick with acceptable pressure levels rather than super-stoking the case you've got to dangerous pressure levels. There's always a bigger parent case available if you want to go faster.

    Both the front-ignition and the duplex/triplex loads are pretty much unnecessary for standard-capacity cartridges with the burn-rate range and number of powder choices that we've got available these days.


    Personally, I tend to think more on the lines of efficiency rather than raw fps for my reloading. After burning out a few barrels shooting prairie dogs and coyotes I've decided that backloading just a hair will make things last a lot longer and still get the job done to make the fur fly.
    How much fps can I get for a given powder charge and how much more powder (and pressure and barrel wear) is it going to cost me.
    Last edited: Dec 19, 2011
  16. JLA

    JLA Well-Known Member

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    Not likely. He just minds one thread. the wildcat 12 from hell thread. Its the only thread he tend to here at TFF. you will have to PM him.
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