duplex loads

[deadeye dick]

Was listening to a new gun related show on my local radio station. One caller asked about duplex loads. I've never heard the term before. Something about mixing powders to create your own load. Sounds VERY dangerous to me.
Can you explain the function of this type of load.

 

[steveno]

I think some of the very first 454 loads were duplex. I think that Elmer tried them also. I think in both instances the pressures were very high and resulted in some blown up guns. I think it was an attempt to get a better performing powder. there wasn't a good reason for it way back when and certainly ain't any reason for it now.

 

[BigBore45]

they mostly used them in black powder/ smokeless conversion cartridges and to tailor a load for one cartridge. kinda like hodgdon leverevoloution powder is really good in the 30-30. but that was a long time ago when they only had a few canister powders available. with all the powders we have today there is no reason to do it. i can be dangerous!

 

[ReloaderFred]

The two powders weren't mixed, per se. The faster burning powder was placed in the case first and then the slower burning powder was placed on top of it. The fast powder was used as a "kicker" for the larger amount of slower burning powder.

It was also used for some of the larger black powder cartridges, where a very small amount of fast smokeless powder was placed in the case and then the larger amount of black powder was placed over it. Again, it was used as a "kicker", and I believe the intent was to get a cleaner burn.

As Big Bore 45 says, there's no need to do it with today's powders.

Hope this helps.

Fred

 

[Salmoneye]

The Ideal #38 Reloading Handbook has some duplex recipes in at least .30-06...

That said, I will never try one...

 

[Slamfire]

I have never tried this. Manufacturer's blend powder stocks all the time to achieve a consistent pressure curve, but with one type of powder, and all lots are chemically consistent because they are made by the same manufacturer.

Blending different powders based on layer cake theories is risky. It assumes there will not be strange interactions between different powders. There may be.

I have seen solid rocket motors which were cast like layer cakes. There was a different burn rate between layers, but, the layers were hard, like cheese hard, and by the time the fire got to those layers, the old layers were gone. Gunpowders are granules that mix well, I don't see how you can keep the layers segregated during combustion. I don't believe that the faster powders will ignite first and then the slower powders. I think ignition is far more complicated than the candle stick model assumed by the Duplex loaders.

And, I have never seen a pressure curve. Don't know what the pressure curve looks like. If small changes result in extreme pressure curve spikes, that is duplex loading is basically unstable and unpredictable, I don't want any of it. The rifle case loads with Blue Dot are an example of this. Alliant does not recommend them because small changes in anything result in a pressure spike. Still there are shooters using Blue Dot in their 223 and other calibers and it does not take much search time to find examples of rifles that blew up with Blue Dot.

Science is advanced by dreamers who test their models and find what works. Bad ideas are dumped and people forget why. Duplex reloading must have been a failure, or we would all be doing it.

 

[PapaG]

We used to subscribe to Dan Cotterman's "American Reloading Association" which published a mimeographed newsletter from time to time. I remember reading the article about Dick Casull and his attempts to make the magnum 45 which ultimately became the .454. He used a TRIPLEX load for some attempts with a base of Bullseye, a middle pile of 2400 and a final topping of Unique. I even remember the numbers but will not share them. BTW, he blew up most of the SAAs he messed with.

 

[ironworkerwill]

When I hear talk of some expert making a duplex load it reminds me of boyhood tales about urinating on an electric fence. I'm not excited about trying either one.

 

[1911 guy]

If you have several million dollars worth of testing equipment and proper safety devices to test pressure curve, gas expansion ratios and velocity at both muzzle and bullet/case separation, have at it. Otherwise, it is a profoundly stupid idea.

This is another artifact left over from black powder days, where it did make sense in some large bore cannon to have a "kicker". This is sometimes still done in some black powder small arms, especially when using pyrodex.

But smokeless is an entirely different animal. How different? Continuing with the animal analogy, think blue whale and squirrel.

 

[GBExpat]

I think some of the very first 454 loads were duplex. ...

I recall first reading about the .454 Casull in the '70s ... the article described triplex loads for the beast.

 

[Doc7]

Was listening to a new gun related show on my local radio station. One caller asked about duplex loads. I've never heard the term before. Something about mixing powders to create your own load. Sounds VERY dangerous to me.

Can you explain the function of this type of load.

Been listening to Tom Gresham eh? I have been listening to his pod cast on my drive to work for over a year a now. 3 hours and the after show gets me through Tueaday night! It is available in the iPHone pod cast app and I recommend listening to archived shows which are well worth it. You can also access it directly via his website if you don't use an iPhone or don't feel like learning a podcast app.

 

[taliv]

i had some success with them in unusual applications. not something i do regularly though.

 

[KansasSasquatch]

There's also duplex shotgun loads. I think they're somewhat popular around here for turkey loads. Something like #6 shot under #4 shot in a 3" shell. I don't know enough about shotshell reloading to know if that's a bad idea or not, but I know a few people who swear by it, and they've killed more turkeys than I've ever dreamed of.

 

[SwaneeSR]

Wow. I have never heard of duplex charges, projectiles -sure.

I think a lot of us can agree with 1911 guy that without the correct lab equipment this is a dangerous pursuit. Also with today's powder offering, not necessary.

I can see the attraction, but the testing!!! You need more than a chrono and a paper target.

Swanee

 

[stubbicatt]

Yep. Some folks duplex 2F and about 5 grains of pistol powder to keep fouling down in BPCR.

 

[PapaG]

Common practice since the early 1900s to put a pinch of smokeless in those bpcr loads. I used 5 grains of DuPont Shotgun Bulk Smokeless under 55 gr of FFg in my 45-70 Rolling block and it shot clean all day long. Have one target in the file from about '70 showing a 3 5/16 group at 200 yards. (I had to screw the receiver sight all the way up from the 100 yard zero, however..maybe two threads holding it in.
I've heard of folks doing it in muzzle loaders but I never would.

 

[TimSr]

There's also duplex shotgun loads. I think they're somewhat popular around here for turkey loads.

Thats what I though about when I read the title.

 

[Walkalong]

As Big Bore 45 says, there's no need to do it with today's powders.

Hope this helps.

This. Y'all be careful out there.

 

[TOOT44]

when I shoot my flint lock with a BP substitute to insure a good ignition I will put 10 grains of 4fg down the bore first. goes off every time. at my club this is what we call a duplex load.

 

[Elkins45]

There is a lot of talk from cast bullet shooters about using duplex loads with the surplus 50 BMG powders in 'normal' cases like 308 or 30-06. The idea being that those powders are normally WAY too slow and won't be over pressure even if you pour the case full can be used to gently push a cast bullet down the bore. The 'kicker' charge is a fast burning pistol powder that essentially boosts the primer to help ignite the slow main charge.

The one absolute essential is that these loads be at 100% density or even a little compressed so that the kicker charges stays back against the primer and can't move around.

 

[loose noose]

I believe that they use a cellulous wad between the charges of powder, however I wouldn't even start to attempt this. I do know of a friend who used to do this, actually he had more money than sense, as far as I know he never blew up any of his guns, although I do know for a fact he shot some loose as a goose.

 

[Saint Dennis]

What Elmer referred to as a duplex load did not involve mixing powders. he attached a tube to the primer flash hole to introduce the flash higher up the powder column. This was during WW II, and he would not discuss it as he did not want to reveal his idea to the enemy. Other folks heard of his "duplex loads" and made assumptions he was mixing powders. He claims he got another 200 fps out of the Browning .50 with lower pressures and more consistency. As we all know, if Elmer said it, you can bank on it.

 

[gamestalker]

I sure do remember duplex loads back in the day. I don't think I ever tried it, mostly because it just seemed too risky for the little bit of gain it might provide in any aspect.

GS

 

[tightgroup tiger]

Yea, I heard of people doing also when I was young but I never played with it. I had no way of predicting the outcome, just to many variables.

 

[Grumulkin]

I've tried duplex loads!

The situation was I had a low pressure load with a powder that filled up the case with no room for more. I loaded a fast powder under the slower powder.

Now I know you'll be disappointed to know I didn't come anywhere close to blowing anything up. I didn't get any improvement in performance or accuracy either.

By the way, if you have to ask how to do it, you shouldn't be doing it.