Powder Duplexing

  • Last Post 15 June 2019
reggleston posted this 10 June 2019

Glad the addition of a small amount of smokeless to BP loads has worked out well for those of you that pursue our sport from that angle.

Just wanted to remind one and all that duplexing of smokeless powders can be very dangerous as is emphasized in most reloading manuals I have had occasion to read during the last 65 years.

From what I have read when you duplex smokeless powders you may very well experience large pressure spikes from the combination of two or more smokeless powder. Best advise I can give for one and all is DON'T pursue this type of activity unless your wish to be carried by 6 for a hastened DEPARTURE.

R D Eggleston

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45 2.1 posted this 10 June 2019

Sage advice for those that don't take the time to learn all that has been in print about such things, but you are confusing duplexing with mixing powders. The factories have men on staff with the proper equipment that do mix powders all the time in production of factory ammunition that people buy and shoot daily. That alone is more difficult than duplexing, which is layering of powders with a different approach than mixing. Duplexing loads started at a time when those facilities didn't exist. That means several people did learn how to do it properly and safely. I expect to die of old age and I've been doing that since the mid 80's. There are several rules, but none of use that do this are likely to put them in print because most people absolutely will not follow instructions.................

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frnkeore posted this 10 June 2019

No one should handload unless they know what they are doing, period.

If you can't do your research, before assembling a cartridge or breech seating one, you will get into trouble, be it BP, smokeless or duplex loads.

10 or 15%, smokeless priming loads are safe, with FFG or Fg BP, using powders with burning rates between AA #9 on the fast end and IMR 4198 or slower, on the slow end.

Duplex loads, in that range, even with BP used for priming, have been used, since smokeless, came to be and you can find those loads in old Lyman/Ideal handbooks.

Just when you think you know it all and have "invented" or learned something in shooting, you find that it has already been done, many years ago and forgotten.


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Hamish posted this 15 June 2019

Bob, Frank,

Outstanding posts, thank you.

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loophole posted this 15 June 2019

Folks like Ned Roberts and J.S. Wolf and the authors of numerous Lyman reloading manuals must not have known anything about safe reloading when they recommended duplex loads over the last 100+ years.  I have been shooting them for only about 40 years.  Of course no one has to use duplex loads.

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