Duplex rifle loads, anyone tried it?

[ZA206]

Basically using two different powders to try to get more performance out of a cartridge.

Lots of variations to try to play with the pressure curves… maybe a fast powder on the bottom of the case and slower powder on top. In theory, the fast powder could ramp the pressure up fast then the slow powder takes over and fills out the curve without really hitting a crazy peak.

I’m pretty intrigued by the concept.

Anyone got experience?

ZA

 

[ZA206]

Oh… and I’m not talking about using pistol powders… I’m talking about using known powders for a particular cartridge.
Example…

223 REM using a 77 SMK bullet.
Varget and H322. You can get about 24.5 grains of Varget under a 77 SMK without issue.

Maybe you could do 10 grains of H322 on bottom with 14 grains of Varget on top… or 12 + 12

 

[Ledzep]

Yeah. We do it every day. I'd suggest dropping the idea in a hurry. There's a pile of know-how and test equipment you don't have and I'm not telling.

In fact, I'd go so far as to say that any advice you get on a public internet forum regarding this subject is worthy of going straight into the trash bin.

You're welcome

ETA: And before you get pissed at me, I'll let you know that in most cases where it does safely work, the "benefits" aren't worth a ton. Juice ain't worth the squeeze, especially not blind.

 

[MarshallDodge]

Hmmm...

How would you keep the powders from mixing?

Wouldn't N540 and some of the other double based powders do what you need, in the example?

 

[ZA206]

Yeah. We do it every day. I'd suggest dropping the idea in a hurry. There's a pile of know-how and test equipment you don't have and I'm not telling.

In fact, I'd go so far as to say that any advice you get on a public internet forum regarding this subject is worthy of going straight into the trash bin.

You're welcome

ETA: And before you get pissed at me, I'll let you know that in most cases where it does safely work, the "benefits" aren't worth a ton. Juice ain't worth the squeeze, especially not blind.

Certainly not pissed! LOL

Just very curious, when you guys do it, are you stacking powders in the case? I’m thinking you’d have to as premixing them would be wildly inconsistent. Do you ever stack ball and stick powders together?

I‘m having a hard time believing that two common 223 REM powders, when conservatively used together, would get dangerous. On the other hand, if someone was gonna throw titegroup in with Retumbo I could see things going sideways in a hurry.

 

[towerofpower93]

I don't see how you could keep the smaller charge of higher-pressure producing powder at the back of the case, where it's designed to start the powder train, unless you put some kind of wad on it. Wouldn't that idea require a compressed load with powder B to ensure powder A was held at the back with the wad?

I seem to recall this question coming up in the ARF reloading section years ago and Tony Rumore or another manufacturer mentioned one of the creators of a big bore AR round messed with duplex loads when starting load dev.

 

[ZA206]

If the case is mostly full, the powder isn’t really moving around. If it’s full or compressed, it can’t move at all under any circumstances (It’s effectively locked into place)

 

[BuildingConceptsllc]

Sounds like a dangerous game to play

 

[roostercogburn98]

If the case is mostly full, the powder isn’t really moving around. If it’s full or compressed, it can’t move at all under any circumstances (It’s effectively locked into place)

I’d be willing to put money on that not being right.

Find some fine granulated sugar in various colors and load a few up. Let us know the end result when you pull the bullet and slowly pour it out. Does it come out in layers like you poured, or does it mix up as the case gets jostled around.

 

[Ledzep]

There are all of the variables that exist for powder A, plus all the variables for powder B, plus all of the new combined behaviors of A+B.

If you don't have a pressure test barrel, properly calibrated cases, and a lab to test at a bare minimum hot, cold, and ambient samples, don't do it. I don't care what quickload or any other program says. It sounds cool but the reality is that you're looking at maybe 50-75fps increases in velocity (assuming available powders are a poor fit-- if the cartridge volume+bullet is a good fit you won't get anything out of it other than added complexity) and in my experience very typically no benefit in precision, ES, SD, etc.

Almost all of the ball powder you purchase is a blend to hit the right performance metrics-- it's done in a lab purpose built for it run by people with collective centuries of experience. They don't tell people how to do it. That's not because of trade secrets-- it's because people without the right equipment trying it are much more likely to get hurt than to achieve any reasonable/meaningful performance increase.

 

[bax]

This is interesting to think about. I'm thinking that "burn rate" is determined by pressure, physical shape, initial state powder chemistry, and the intermediate products and specific reaction times - for example, base compound X, in the shape of a sphere with initial surface area Y, converts to intermediate products A, B, and C at a rate determined by pressure which is a function of initial shape and surface area - not that exactly but something like that. If you introduce a second powder, you have different response to pressure, perhaps producing different intermediate products or in different ratios, and the reaction chains release energy in new ways.

My dad was a research chemist. When I was in high school, there was this girl. My dad was in research. Her dad was a production QA chemist. My dad and his friends knew about her dad - he was the guy at the product plant who blew up his lab. Blowing up your lab was frowned upon. They didn't socialize.

 

[ZA206]

There are all of the variables that exist for powder A, plus all the variables for powder B, plus all of the new combined behaviors of A+B.

If you don't have a pressure test barrel, properly calibrated cases, and a lab to test at a bare minimum hot, cold, and ambient samples, don't do it. I don't care what quickload or any other program says. It sounds cool but the reality is that you're looking at maybe 50-75fps increases in velocity (assuming available powders are a poor fit-- if the cartridge volume+bullet is a good fit you won't get anything out of it other than added complexity) and in my experience very typically no benefit in precision, ES, SD, etc.

Almost all of the ball powder you purchase is a blend to hit the right performance metrics-- it's done in a lab purpose built for it run by people with collective centuries of experience. They don't tell people how to do it. That's not because of trade secrets-- it's because people without the right equipment trying it are much more likely to get hurt than to achieve any reasonable/meaningful performance increase.

Why do you guys fiddle with it if it’s not worth the trouble?

 

[Ledzep]

Why do you guys fiddle with it if it’s not worth the trouble?

It's fine with proper testing, but mostly because of the scale at which we buy powder and we have a plethora of bullet weights and cartridges and specifications to meet.

 

[KYAggie]

I’ve used a small amount of black powder to ensure a good light off of Triple 7 in a percussion BP gun and it worked great. Velocities were higher than Pyrodex, but at the range you had to swab with a wet patch between to cut down on the Triple 7 donut.

That’s as much duplex loading as I’ll ever attempt.

 

[Ex E6]

Common in black powder kickers .

In smokeless powders NO NO NO . Simple explanation a different powder does NOT occupy the same space aka volume ,even if it's next door on the relative burn rate chart . Not all powders are manufactured alike the surface burn area is an unholy animal Not to be trifled with , volumetric expansion pressures are DANGEROUS enough .

Volumetric burn calculation becomes DICEY at best . I tried it once in a 12 gauge hull and lived ,I also had a test barrel with a piezo gauge ,it wasn't a consistent measurement . IMO ,IF there was substantial velocity or any accuracy gain and safe , One of the manufacturers would be producing ammo using it .