[P95Carry]

Everything suggests that duplex loads are bad ju-ju .... and I have no real wish to even experiment. Now and again tho someone comes up with some ''pet'' formulation. Strikes me as dangerous but .. is that concern fallacious?

Bottom line ..... do any genuine recommended duplex loads exist? Pure curiosity .. that's all. So many powders out there ... hard to see how any possible advantages.

[Gewehr98]

Because the black powder/smokeless duplex loads have even been accepted for use in NRA BPCR silhouette matches. It's what I use in my ancient Rolling Block Creedmoor restoration, basically a few grains of smokeless under the main black powder charge for improved ignition and less fouling. Not exactly authentic, but a bit easier on cleaning and shooting long strings of black powder cartridge rounds.

Or are you thinking of all-smokeless duplex and triplex loads, like Dick Casull used when working up his .454 Casull loads from their humble .45 Long Colt beginnings? Yow, those were serious stuff!

[Mike Irwin]

Yes, I believe that Ken Waters has had some duplex, and even triplex, loads listed in his articles from time to time with HUGE warnings.

I believe in years past George Nonte also had some loading information with duplex loads, but I may be wrong about that.

Duplex and triplex loads can be very safe. It's just the working up procedure that can be kind of hairy.

Ultimately, though, duplex loads should ONLY be shot in the firearm for which they are developed. Every firearm is a different creature, and duplex loads can angry up that creature.

[P95Carry]

Ahhh ... now Gewehr's mention of the smokeless/BP mix does ring a bell .. I was thinking rather narrow regarding just smokeless only.

But yeah - then of course Dick's work up loads ... was not sure if this was legend or fact.

I guess you are spot on Mike re development for just the one gun ..... must need an inordinate amount of experimentation ... and care!!

I didn't mention before but I did sorta use a duplex of my own some years back .. in as much as .. I put some 2400 powder in a hopper to top up .. then realizing it still had some red dot left ... sheesh ... they don't even look same!

Anyways .. I emptied the whole lot out and was going to pitch it ... now I hate waste! Instead I worked on the assessed basis that it was a 10:1 ratio . 2400:red dot .. and so mixed it throughly .. and used it up for some approx 44 spl loads. In essence ... backing off from mag loads, per 2400 ... and reducing the charge. I went on the safer side of estimation ... and in fact they were an acceptable round ... used up for plinking thru Redhawk.

[Mike Irwin]

A 10 to 1 ratio of a pretty slow powder to a pretty fast powder shouldn't be a problem, but you never know.

If I did that and it was Red Dot and say, 231?

Into the garden.

[Quantrill]

IIRC, when the initial triplex loads were written up, I think it was a combo of Bullseye, Unique and 2400. At the time the article was written, it was stessed that these powders were not mixed together but rather stacked one atop another like pancakes. Quantrill

[Mike Irwin]

Good point, Quantrill,

Duplex and triplex loads are very rarely "blended."

[P95Carry]

One further thought ... if ''stacked'' .. unless a compressed charge, or close too it .. how is inter-mixing within the case avoided? Are thin separators used maybe?

I assume too that the principle behind the stacked approach is a theoretical sequential burn - but what rationale can we have there? Fast, thru medium to slow ... or vice versa?

[Gewehr98]

Maybe the idea is to flatten out the burn curve, less of a peak, so that the propellant stack is providing uniform thrust from ignition until the bullet leaves the barrel? :confused:

[P95Carry]

Maybe the idea is to flatten out the burn curve Certainly with long enough barrels Gewehr that could probably work ... which would suggest the sequence ... slow-medium-fast .... hmmm.

Well, let's think pressure curve .... smaller sustained peak pressure maybe. What you are meaning I think by ''burn''.

[Rico567]

From everything I have ever read about duplex loads, there are people on this thread who are braver than I'm ever gonna be on this subject....accidentally mixed powders make great fertilizer, since they are VERY high in nitrates. Do your flower garden a favor.

[Jim Watson]

Gewehr98

I have only been shooting BPCR Silhouette since last Spring, but smokeless-black duplexing was not allowed then and the 2004 rules do not allow it for Creedmoor at Raton.

Duplex is still allowed for BPCR Target.

It was very common in the late 19th century for Schuetzen loads.

All the (few) duplex powder loads I have ever seen are properly loaded in layers, not blended. That is done by making sure the total charge is compressed, so the different powders can't sift around.

I think it was Robert Hutton who did the shooting for the military in the development of the .223. He was loading ammo at the range, blending powders to get the velocity of a .222 up to what was planned for the .223. He always said the blend of powders required to get a .222 to penetrate an army helmet at 300 yds was classified.

I haven't seen any duplex loads in Ken Waters' articles but Bert Shay did a good deal of work with them. I'll check Phil Sharpe tomorrow.

[Mike Irwin]

.. ...

As I said in a previous message, duplexed, or blended, loads should be used ONLY in the firearms for which they are originally developed.

Switch to a different firearm, and the development process beings all over again.

[Mike Irwin]

Jim,

I may have my authors mixed up. It's been years since I've read much on this subject.

[Johnny Guest]

Y'ALL ARE DOING FINE on this topic.

A while back, there were some specific "blended" powder loads mentioned and I, as moderator, made the executive decision to not allow 'em. I'm fine with the abstract discussion of blended and duplex loads, but, please, no specifics on this board.

As has been pointed out above, each such load MUST be worked up individually, for the particular firearm. I realize there has been some very scientific workups done, but I ask that you discuss those in private. :D

Thanks to all.
Johnny

[John Ross]

Do a Google Groups search for "Norman Johnson" and "duplex" or "H870".

JR