Would like to know if any of you have ever gone into duplex or triplex loading. Any interesting results? roger

NO; no one does that since the 60s when the .454 Casull was invented; he decided it wasn't worth the risk.
I am willing to try anything but not that. You are playing with fire, literally, if you do.

In my young and stupid years. We did load a duplex black powder in 45-70 and 45-90s. Just a couple grains of smokeless. Seemed to burn just a touch cleaner. They were replica Sharps. I've also seen a couple black powder shooters use a black powder in front of pyrodex. They said better ignition.

Wouldn't do it now days. Did a lot of things in my 20-30s that sound really stupid now in my 60s.

Yes,and have for 45 years now. On large caliber,large capacity cases. My .50 Alaskan .45-120 and my 20mm.
Duplex are used as an ignited charge only and add little to the maximum chamber pressure as the load is factored in.
3 grains for the smaller calibers noted,ten grains for the 20mm.
The functions that it servers is to create heat and a small pressure wave traveling through the charge to aid in a cleaner burn,which it does very well when used with a very slow powder.
My loads are nothing new for the 50 and below. Old info from tried and true charges.
The 20mm load was worked up while I worked at HP White Labs in the 80's.
All are safe never exceeding a safe chamber pressure.

Years ago I came into a copy of Rocky Gibbs book. His duplex load data was somewhat intriguing to say the least. I tried a couple times with a 280 to duplicate what Rocky claims he saw.

Gave it up.... couldn't get anywhere close to what he claimed.

i've used duplex loads for years - yup - one in the right barrel and one in the left i just knew you were looking for an answer like this -wanna hear about the drilling loads

Funny,
Now, as for duplex in Black Powder loads; yes I do it routinely; I use ten percent 5744 under a BP load. Tests by Lyman have proven it quite safe up to ten percent; no more.
BUT; I advise never do it in smokeless loads.
Pyrodex; best used a lawn fertilizer; it is pure crap as a propellent. When it came good out in the 70s, I thought it was going to be a BP substitute; turned out to be junk and I still have some of it. Anyone can have it if they come and pick it up.

We use duplex loads for the .700 NE.
As we were encountering hang fire.
About 3 grains of BULLSEYE at the bottom of the charge cured that.

My first venture with duplex loading was in black powder cannons I once built, These ranged from .500" to 1.250" bores. This was around 1959. It was done to get cleaner burning. At the time I thought it worked but today I just don't know.
Having read Frank Barnes's Cartridges of the World( first edition ) and his experience with duplex and triplex loading I thought I'd give it a try. Everything seemed to go well for many years till I got some 5010 and 5020. No cartridge I had with the heaviest bullets would burn all the powder put in it. That included my .358 X .375 Ultra mag. IMP.
A little side note; Someone asked " If you get all that powder to burn how do you know you haven't got too much already?"

Well I worked with a number of rifles with duplex loads and the 50 Cal. MG powder with not a whole lot of success.
I was working with a .22-250 increasing the fast burning powder a grain at a time with a near full case of 5020. I must have hit the temp. and pressure threshold . A chunk of the rear end of the case was blown off, what was left of the primer pocket was 2 x bigger in diameter, the case was brazed to the bolt and the bolt was cracked. The rifle suffered severe set back. The shooter ( me ) only suffered minor facial burns ( gas or vaporized metal ) . My glasses saved my eyes from harm.
I look at the 8# jugs of 5010 and 5020 from time to time and wonder what to do with them. Duplex loading just ain't the answer for me. roger

I wasn't going to post this, as we tend to do rather crazy - some might call stupid - things here sometimes.


But, We did try to make our own powder mixture a while back while loading a hot wildcat.

What we found was that some powder was slightly too fast, and another too slow for our purpose.

Great kinds got together, and we decided to mix the two powders in varying quantities.

We did not get any appreciable increase in velocity at all, so common sense prevailed.

We get a lot of ammo that cannot be fired. Mainly due to it getting wet, and the primers getting corroded.

This includes all sorts of calibers, but mainly 7.62x39 Russian and shotgun ammo in varying types.

We always recover the powder.

The powder from the 7.62x39 Russian we use for loading the .223 Remington.

The powder from these can vary from flake, stick or ball powder.

WE mix the whole lot together, and use it in loads for the 223 Remington.

The recovered powder from the shotgun ammo we use to load pistol ammo.

Mainly .38 Special, .357 Magnum and .44 Remington Magnum.

Never had any problems at all.

Some here summarily dismiss use of duplex loads as " dangerous" perhaps out of ignorance.

Some years ago we had a problem in South Africa with lack of appropriate propellants for certain cartridges. Our line up from "fast to slow" had few options with then resultant large gaps inbetween.

So at one point a lot of big bore shooters were playing with a variation of 458 cal wildcats based on either full length of short versions of the 404 and the 416 Rigby.

They went by a number of names some unbeknown to the "inventors" were actually duplications of other existing versions... Stuff like the 450 African express, The Vincent short and Vincent long, the 458 Short Majoor and the long Majoor to name a few.

What was a problem for them all was lack of appropriate burn rate powder.

So Johan Loubser then of Somchem ( now a ballistician at Western Powder) came up with a solution where one would mix up two adjacent powders in the burn rate line up to get to the correct "inbetween mix".

Many guys used this successfully for many years without any problems. I do know of some isolated instances of guys seeing pressure problems but they were also related to loading heavy for caliber bullets with long bearing surfaces.

Remington used to sell duplex loads. 12 gauge 1 1/8 oz. 7 1/2 & 8's.