Duplex loads, Mixed and Reversed Powder Charges

[@Everythingblackpowder]

Sorry folks, I neglected to mention that there was no noticeable difference in fouling between all of these loads. They all burned exceptionally clean.

[@wyatesbob]

Thanks that's good to know.

[@perianmarcel2059]

Hello! That's exactly what I was about to ask. Great video and interesting!

[@unclechaw1894]

This kind of reminds me of how modern artillery shells still use a small amount of black powder to ignite the larger powder charge.

[@cupajoe7258]

It's the reason why Goex is a thing. It's a propagation powder for artillery.

[@Everythingblackpowder]

That’s what I hear

[@gb123-ej8wh]

I know artillery uses BP but is it duplexes with smokeless for real? Does it depend on the gun size? I remember watching them 155 Paladins firing and lot of visible flash and smoke and THUNDER

[@krockpotbroccoli65]

​@gb123-ej8wh The 16 inch cannons on old battleships used duplex loads. Same thing. Small ignition charge of BP with an absolute metric shit ton of smokeless on top.

[@the_great_tigorian_channel]

I have heard that as well but I figured that was more of a reliance sort of thing more than a velocity thing. Black powder has a "liquid" phase when it burns that allows it to retain intense burning heat for a comparatively very long time when stood side by side with smokeless powders. (Which is why it burns faster in open air as it can hold the heat of the reaction closer to itself and other unreacted black powder particles) I figure it's that extended duration of intense heat that guarantees that the smokeless powder will go off more reliably even in less than ideal situations where quality may have been potentially compromised.

[@Royal-xh8db]

The way I understand it smokeless powder burns faster as the pressure rises. The black powder gives your initial spike in pressure, then the smokeless powder ignites and stretches your pressure spike out further after your pressure is already up.

[@robertstump4740]

You and several others have an answer that makes the most sense. Smokeless on the bottom has to make its own pressure but if on top, it gets to ride the wave of pressure from the bp charge.

[@gaslyktan]

Well put. 🙂.

[@davisrs1]

As a Chemical Engineer, that's the way I have always done it!

[@tedfries8970]

Your latest duplex 303 is very interesting, great job!! You neglected to say how clean the upside down load was. This is my only thing that is of interest for myself other than the consistency. Thanks Willard. Another great video. Ted

[@Everythingblackpowder]

Thank you. There was no noticeable difference in fouling in any of these loads. All were very clean

[@claydallen5308]

Im surprised the "upsidedown" load made such a difference! Thanks for the info! 👍

[@tsclly2377]

Ya.. do note the primer results, perhaps this will do better with lighter bullets (150 grn.) [paper patched in 30-40 Kraig out of a Winchester 1894 Carbine (note that .303 Brit can be resized to 30 Government)]..

[@dangeary2134]

Kinda like a “second gear” before the round gets out of the barrel! Very interesting!

[@rayc.1396]

I have payed with duplex loads for years, A gunsmith by the name of Rocky Gibbs got me interested in. He used all kinds of techniques with a lot of different powders and other things, but they were al smokeless powder loads. He used a charge of rifle powder on top of a charge of pistol powder and vice versa. His explanation for the faster FPS of the pistol powder on top was that the rifle powder had moved the pistol powder down the barrel before it ignited and gave the projectile a powerful boot because it couldn't over come the pressure of the rifle powder and therefore the pistol powder exploded on top of the rifle charge and boosted the pressure rapidly near the end of the barrel. I tried many of his loads and one thing I will say, the crack of the rifle is way different.

[@M.M.83-U]

The effect of the upside down is surprising, thank you.

[@Studentofthegun45]

From Elmer Keith’s Big Game Hunting: “The whole principle of Duplex loading is to compress the powder charge in the case with no air space. The case must be the right capacity for the bore, bullet weight and powder rate of burning used. Further it must have the right constriction at the shoulder for best results. Next the chamber must be tight over the body of the case to prevent undue case expansion that would in turn allow the fire to burn back around the bulk of the charge. Then with a tube in the case, and the primer flash carried forward to the front half of the charge, the forward portion of the charge is ignited and a relatively small portion of the total charge is used to start the bullet. After the bullet is in motion you can burn a hell of a powder charge behind it with normal pressures.” Just thought I’d put this out there in case yall hadn’t seen it! It’s a very cool ordeal.

[@rjoetting7594]

I used to have a few older reloading books from the late 60s and the early 70s that listed some black powder duplex loads, and the whole purpose wasn't to get more velocity but to get cleaner shots. Some of the early black powder enthusiasts had lost the knowledge of the early black powder loads. The main loss was a proper lubricant for black powder, and after a few shots, all accuracy was lost without cleaning the barrel. But duplex loads allowed more shots between cleaning the barrel. Some of Mike Venturino's articles talked about this issue. In his early days, his experience with the Sharp's rifle and accuracy problems he had.

[@marty0027]

Ok😮

[@Sideshowbobx]

Like an artillery shells powder train - a line of blackpowder ignites the main NC-powder charge in a flash. Pressure spike and flat primers go together as I would have predicted - nice. Once again, great on the video.

[@4570duplex]

Another outstanding video that didn't suck! That, and I just don't want to have to make my own damn video... Thank you for going where most of us have feared to tread. The mixing and upside down stacking have both been "off limits", for alleged "safety" reasons, for as long as I have been loading duplex loads. I never dared even try, for lack of any published results, advice, or any sort of encouragement. I'm not sure you realize just how relatively "ground breaking" your efforts are on this front. Very, very interesting results. I think the mixing of the powders was the most vehemently recommended against, with everyone convinced they were going to blow up their guns. To see your results, and just how inconsequential mixing the powders proved to be, pretty much puts all of that unsupported, untested "advice" to rest. Thanks for that. Surprising, too, are the results from doing it "backwards". That kinda forces us to rethink a lot of what we thought we "knew" about all of this. Ah, the vagaries of internal ballistics... So, I have to wonder (keeping in mind your theory regarding the placement just below the bottleneck), how a straight walled case would react to an "upside down" load? I do know that bottlenecks and straight black powder don't seem to get along very well, with what I have found to be significantly increased fouling in the throat area in cartridges like the .44-77 and .44-90. I actually gave up on both because of those fouling issues, following the lead of the Sharps rifle company when they phased them out in favor of straight walled cases. There has to be some weird dynamic with that bottleneck, as evidenced by that fouling (in straight black loads) and your discoveries regarding velocities. Once again, the vagaries of internal ballistics...

[@Everythingblackpowder]

Thank you

[@GenderSkins]

The reversed duplex load actually makes a lot of sense as to why it would produce higher velocity, as it is basically a military duplex load. Meaning that the slower burning powder had more time to build up pressure as it burns, before it hits the faster burning powder to introduce a power spike. In a sense it would be like burn normal gasoline to obtain your take off power to get up to speed, before you introduced nitro s-oxide. Putting the smokeless at the beginning, is like using nitro s-oxide to take off all you would do is spin your wheels before you caught traction resulting in being at your power curve sooner then later.

[@slcgrgcrgcaneafgugiesclawhfg]

Artillery shells have been loaded like this since WW1 or earlier. Initially it was because the smokeless powder wasn't that great yet - but then they discovered that even with good powder this just works better

[@A.R.American1]

I really like these videos I also like the idea of the ease of cleaning using duplex loads.

[@RichardMartin-u8e]

The upside down load for a bottle neck cartridge and its increase in velocity is very cool.... but given Jakes hypothesis on why this is evident for the 303 would suggest straight wall cases would not benefit from an upside down load and the increase in velocity. Sounds like more testing is required to prove the benefits are also realized in straight wall cases...

[@randyhavard6084]

The more GOOD information out there the better, thanks

[@ronrobertson59]

Remember the 303 black powder cartridge was fired in the Lee Medford and Long Lee Enfield not the SMLE No.1 MK lll. Both the Lee Metford and the Long Lee Enfield had a longer barrel.

[@MemorialRifleRange]

Thank-you I did not expect the smokeless on top to be the faster.

[@bobgyetvai9444]

The smokless pressure overcame the blacks pressure and compressed it burning it hotter .

[@mkshffr4936]

This is great stuff!!! I am even more excited to see the pistol caliber version.

[@TeamZcan]

Well, interesting. As a rather old timer it never occurred to me that anyone would ever load a duplex round with the smokeless powder on the bottom!

[@Johnny-jr2lq]

Yes I was completely destroyed in a few forms asking about this subject. You talked about how people act when the subject is brought up in your first video on the subject. I have to say I’m so happy that forums are being more and more irrelevant.

[@Everythingblackpowder]

I hate to say it but I have a strong dislike for forums for that reason

[@robertstump4740]

Agree, forums are a great place to find stupid opinions.

[@Everythingblackpowder]

I’m not saying that everyone on forums is a jerk, but if you are a jerk there’s a good chance you are on the forums.

[@slcgrgcrgcaneafgugiesclawhfg]

Happened to me too, not like it changes anything I make or do

[@loupuleff571]

very, interesting video thanks for listening to all of the crazy ideas and trying them out !!

[@Everythingblackpowder]

You bet

[@bradkuz76]

Great stuff boys! I thoroughly enjoyed all the "duplex" info. Thanks!

[@Everythingblackpowder]

Thank you

[@Friedbrain11]

The reverse duplex load is the way I would load it. It made no sense to me to put the faster burning powder in first. Just something I sensed rather than having empirical data to explain. It is in my mind that the pressures are maintained further down the barrel and therefore higher speeds are out of the barrel.

[@tomektomaszewski401]

Bardzo interesujący film Jake. Dobra robota! 😀

[@richarddean3154]

It is nice to see your mind working as you read the chronograph - wondering what is happening on the fast/slow shots. Fascinating.

[@Travisty_in_motion]

The best way I can explain why the "upside down" duplex load works better is that the final "kick" from the smokeless happens when the bullet has momentum at the end of barrel travel, rather than at the start when the projectile is at rest. Think of the previous duplex load as putting your foot to the floor on a gas pedal and then letting off. The upside sown is like rolling forward with 50% throttle then flooring it for a bit. My question is what if you put just enough smokeless on the bottom (just enough to cover the primer hole so that ignites first getting the black powder to temp to burn clean), blackpowder, then the remaining smokeless on top. I think this might even the momentum down the barrel and give even faster results.

[@tville7043]

Good show thanks for the good info. Are you still gonna do a video of how you make the Black powder using charcoal. I'l be looking forward to your next videos of course but I sure enjoyed watching and learned a lot from the 303 experiments you did. Later. God Bless. NW ga.

[@rnssr71]

nice vid. appreciate your work.

[@wyatesbob]

I like how you test the different possibilities. Very informative and helps us all out. I know you hate subs but 777 would be cool to see in 303 just once. Again great video 👍

[@CF23583]

Great Result! Totally unexpected. Keep up the good work! I wonder what the result will be with a reverse duplex-BP load...coarse-slow-rifle-BP to start with fine-fast-pistol-BP on top? Maybe worth one more test with the 303? ;-)

[@oregonoutback7779]

Being well into my 70's now, I am well past the capabilities for Duplex Loads. Those are so far in the rear-view mirror, not sure if they were actually a real thing or just another fishing story 🤔 Either way, these are fascinating science experiments you young whipper-snappers come up with 🧐 Love watching, as well as digging up memories from my foggy past. Thank you for both 🥳

[@nelsonmackinnon-chobotiuk6862]

This is actually a cool and educational channel, I got into black powder a bit ago and he has "sparked" my interest 😂😂

[@Everythingblackpowder]

Glad to hear it.

[@donakahorse]

comment for the toooob algorithm. That worked out about like I supposed it would except the upside down load. That surprised me. Thanks for this

[@donakahorse]

also, will it make as much of a difference in a straight walled cartridge. curious

[@Everythingblackpowder]

Thank you

[@robertstump4740]

Fascinating results, never thought to try this. For us old BPCR shooters, smokeless was always in the missionary position.

[@the_great_tigorian_channel]

So here is my best (very unprofessional yet lengthy) guess as to why the upside down load was achieving higher velocity: black powder burns far more gradually and steadily than smokeless and is more like a push than a punch. When you mix in smokeless evenly you get slight bursts or spikes of energy in the burn's timeline. Those spikes in energy or pressure may deplete or be relieved as the bullet moves down the barrel providing more and more volume for those little pressure spikes to be relieved (perhaps creating a "speed up and slow down" effect as the bullet travels down the barrel"?). However, when you load the smokeless powder on top in an upside down configuration the steadier burn of the black powder builds up as it would with a straight black powder load and finishes off with a crescendo of all the smokeless going off at the end rather than spread throughout the burn in smaller bursts. Like a running start before punting the football. Or... perhaps something to that effect. Like I said, I am no expert, but I figure that may make some sense.

[@tullyhowell1624]

Old very known use of. RED DOT powder. 1=5. (1 grain red dot = 5 grains blackpowder) for use in target rifles of 45-70 40-60 38-55 ect. Mixed. Generally. One shot glass reddot to a pound of black powder , the duplex of smokeless near the primer was called a "kicker" of a burn rate powder. Of 4227 or so behind a very very slow smokeless or black powder. Now mixed smokeless is the original "duplex". The theory is the higher nitro content has extra oxygen to help with the burn . It just so happens 13gr reddot equals 65gr black in velocity ,( pressure not withstanding) , green dot and unique also works , many high nitro powders ( fast work well ) Bullseye the highest nitro content

[@Sonriah4145]

Upside down should "in theory" also be safer. Because the black powder has pushed the round part way down the barrel before the smokeless is triggered, the smokeless pressure is applied to a larger area meaning the maximum actual pressure should be lower. This is assuming the black powder doesn't burn to the smokeless before the round starts moving, so "theoretically" also this was fun to watch, thanks for testing it.

[@adambarlow7787]

I don’t really think that theory holds out as he had flattened primers with the upside down load…

[@thetraveler5798]

Actual Research when the minds get together, "Love when a plan comes together". the AZ-Team 😁❗👍 😎🤙

[@steveshoemaker6347]

Very interesting.....Thanks to all of you guy's..... Old F-4 Shoe🇺🇸

[@dtaggartofRTD]

If the smokeless on top shoots well that seems to produce very nice results. Definitely a load to work up on though given the pressure signs. Really cool to see a load that can replicate the original velocities without compression shenanigans. Fascinating to see how position of each charge affects the outcome.

[@WeaponsAffair]

Very interesting. You addressed all my speculation, in regards to these duplex loads. Excellent as usual sir!

[@Everythingblackpowder]

Thank you

[@MulletDestructur]

I’d say your results when measured with modern chronograph equipment are well within margin of error when compared against 1890’s-1950’s vintage speed measuring accuracy.

[@knight0334]

Your small smokeless over a main BP resembles my experience with a fat smokeless main charge under a smaller faster powder on top(also smokeless) in .45-120. I have a .32" barrel, and my best guess is that the slower big main charge is pushing the faster burning top charge down the barrel, then igniting it there - helping to keep pressures up in the long barrel. Juggling charges around I was able to push a 300gr .458" JHP to about 2800FPS. ....my groundhog vaporizing round. I'm not going to give out duplex loads in public for liability reason. But my main charge was an IMR-4198, and the top charge was a smaller pistol powder charge in the 10% to 15% range of the main powder.

[@knight0334]

And BTW - I love what you post on here!

[@shaunharvey1112]

Bp is first gear grabbing 2nd when it gets to the smokeless

[@kbjerke]

GREAT stuff, Jake!

[@Everythingblackpowder]

Thank you

[@pink_love_cat4928]

Great video I've thought on this subject for some time now so you've cleared up some of that for me

[@luuk-out-below9804]

Interesting as always!

[@Everythingblackpowder]

Thank you

[@TUCOtheratt]

So, the first batch smokeless under BP showed some higher pressure flat primers but what about the mixed? Did they have flat primers?

[@Everythingblackpowder]

The smokeless on top of the BP had flattened primers. More so than the mixed and BP first loads.

[@VONBOYD2]

Damn I've learned so much from you!! Keep doing what your doing!! We all appreciate your studies

[@Everythingblackpowder]

Thank you

[@comentedonakeyboard]

Interesting mix

[@Walter-wo5sz]

Great video.

[@Everythingblackpowder]

Thank you

[@jeremyp2295]

Here's my theory on the upside down load. I think the blackpowder developed enough pressure to make the smokeless powder to ignite properly. Smokeless is designed to do its work under more pressure. I wonder if it would react differently if it was ignited by a magnum primer. In the theory that it hits the base of the powder column harder as it ignited and moves into your theory of the effect of the bottle neck. And would it act differently in a tapered case like a 45-70. Love this science stuff. You keep me thinking.

[@TomGellos]

45-70 is straight wall

[@jeremyp2295]

@@TomGellos it's a straight tapered. They were designed with a slight taper to aid in extraction from a fouled chamber.

[@TomGellos]

@@jeremyp2295 it's refered to as a straight wall brass case I have one in my hand I don't see any noticable taper, and if you need a dial caliper to see the actual taper it's not going to be of any significance.

[@jeremyp2295]

@@TomGellos the case tapers from. 5055 at the rim to .480 at the mouth. It was significant enough for them to keep the taper in the final design. As things moved into the smokeless era they stopped calling it a straight tapered case

[@brucecoleman1509]

Wonder how that would work in shotshells.? Very interesting . Great video. 👍

[@d3faulted2]

I wonder if people using duplex loads was less about performance and more about how cleanly it made the cartridge burn. Less fouling might mean more accuracy for long strings of fire. Also the early smokeless powders would me much less stable than what we have now. Things like cordite and Poudre B burned really hot and fast if i'm not mistaken. Something that would be interesting to try would be flash paper instead of smokeless powder. It is basically straight nitrocellulose. It might emulate the early smokeless powders better.

[@EastBayFlipper]

This makes sense🤔 from a combustion/deflagration view of the 2 propellants. The black powder will decompose faster than the smokeless, initially however, the carbon/sulfides generated could be flash-coating the smokeless powder and creating a delay, when the smokeless is on the bottom because the burning front follows the propellant and the "exhaust" is in the back before it's in the front. This also meant the smokeless on top was combusted, uncoated by residue from the black powder because it was defligrated by the flame front directly. I love your videos ❤ The experiments, within reason😂, are fascinating. It took me a bit to puzzle this one out but based on similar studies, this is a reasonable possibility. Mega cool That coffee grounds powder was no Espresso tho😂🤣😅👍🍉

[@davem4169]

Excellent

[@curly__3]

Super, ultra cool video! Thank you.

[@Everythingblackpowder]

Thank you

[@RustyJoe]

Very interesting results! Keep up the good work. I’m curious if the reverse and blended loads were as clean as the conventional duplex loads?

[@Everythingblackpowder]

There was no noticeable difference in fouling between all these loads

[@RustyJoe]

@@Everythingblackpowder that is interesting and maybe a little surprising. That’s food for thought 👍

[@cal9064]

An interesting experiment. Another thing to consider might be the proportion in grains of smokeless used. Compared to black powder. With 5 grains of Bullseye....though a faster burning powder.....only around a half of that used in the other duplex loads. That may also have some effect on total velocity and energy figures. Regardless, it does prove one thing: duplex loads can be useful.

[@ricktaylor5744]

Interesting, thank you Jake!

[@Everythingblackpowder]

Thank you

[@chuckaddison5134]

A very interesting video indeed. I would not have guessed that the 'upside down' charging would have made that much difference. Try it in a pistol load to see what it does there.

[@hazcat640]

Interesting as hell!

[@Everythingblackpowder]

Thank you

[@loquat4440]

Brilliant

[@wagon9082]

Good video

[@davidgiffordsr.930]

Thanks. That was interesting.

[@ScottTyson-s7u]

I was curious and tried to repeat your experiment in 45-70. My duplex is 5grains of 5744 and 60grains of 2X Goex. Both sets used were topped with a 500 grain bullet all within 2grains of weight. My bottom loaded rounds recorded an average of 1231.25 fps and the top load was 1262.75fps for an increase of 31.5 fps. Point of impact at 100 yards was not dependable. One observation was that bore had less residue with the bottom loaded sequence. Thank you for the video. Just sharing my results.

[@Everythingblackpowder]

Interesting. Thank you

[@soylentgreen7074]

I don’t know the science behind duplex loads and I’ve never attempted them. I would expect the ones loaded with the black powder first separated from smokeless should do better that’s how naval guns and artillery are loaded. The black powder is used as an ignition for the smokeless charge.

[@richarddixon7276]

A very interesting video , Thanks for all Your hard work , it would be really interesting to see if You could get better results using some of Your home made BP , the Coffee grounds would probably benefit most from using a duplex load . Thanks again , catch You next time . Shoot Straight Stay Safe & Stay Well .

[@Everythingblackpowder]

Thank you. I recently loaded some duplex 44/40 with some homemade cotton powder and it performed really well.

[@terryqueen3233]

Thank you

[@herbertgearing1702]

To me it seems like the art of finding the perfect powder load is about getting the projectile to slowly build velocity all the way to the end of the barrel by gradually increasing the pressure. If the powder is all exhausted significantly before the exit you can lose speed and accuracy and if the powder is not completely burned before exit you have significant muzzle flash and unburned powder fouling. This has to be balanced and limited by the amount of pressure the barrel and cartridge are capable of containing. I think these results are down to the black powder first arrangement allowing all the powder to burn by igniting the slower powder first and the faster powder second. You may be around the limits of what you can do with this in the 303 but it makes me wonder about something like 45/70 and other big slow black powder cartridges and adding a little topper dose of smokeless to boost their velocity. The reaction happens so fast inside the barrel that from our perception it's instantaneous but clearly the timing is more important than I would have assumed or the mixed loads would give the same type of results.

[@vicroc4]

Your speculation about finding the perfect powder load isn't far off. It's why there are different burn rates of smokeless powder, so you can cater where that maximum pressure spike occurs to your particular barrel. Handgun powders burn fast so that they've generated all of their pressure in a stumpy barrel. Magnum rifle powders burn slow because there's a lot of powder and they want to make sure that it doesn't just spike the pressure and blow up the barrel. (The consequences of using too fast a powder in a large rifle cartridge are amply demonstrated by Kentucky Ballistics' infamous accident with a .50BMG rifle)

[@bjoernkraft4483]

If sulfur and saltpeter are ground together before mixing with charcoal in the ball mill,can it lead to a different behavior of the black powder? I'm also considering other experiments where saltpeter and charcoal are mixed first and sulfur is added later in the ball mill, and more to explore the other possibilities Liebe Grüße aus Deutschland 👍

[@Everythingblackpowder]

I get the best results by milling all three components together for 24 hours

[@bjoernkraft4483]

Thanks❤ Dankeschön 🙂

[@Slowly_Going_Mad]

If I had to take a guess it's probably that smokeless has a longer run-up time when burning (basically just burns like RC fuel unconfined) while the black powder has a really short run-up time. The black powder acts somewhat like a booster to supply the heat and compression to fully take advantage of smokeless powders true power basically short cutting the hang time in ignition delay. The pressure curve would probably be the signature spike from BP followed shortly by what you'd expect from the smokeless but, adjusted for those burning conditions.

[@nigelkavanagh2048]

Interesting vid again sir, something too ponder on.,, 👌👍

[@Everythingblackpowder]

Thank you

[@gb123-ej8wh]

There are also duplex loads using two different powders not necessarily black and smokeless.

[@gb123-ej8wh]

This is interesting. I think I might have strapped the rifle down and fired before risking my face on it.

[@Everythingblackpowder]

I like to live dangerously

[@gb123-ej8wh]

@@Everythingblackpowder I see

[@Everythingblackpowder]

Spare me the safety lecture, Friend. As you can see, it worked out fine.

[@gb123-ej8wh]

@@Everythingblackpowder I’m not getting onto you Willard. Just saying I don’t take risks personally anymore. I think you’ve caught it so much that it’s maybe not that clear. I dig the channel and thanks to it I have made my first homemade 200 grams of powder. Shoots well when charged by weight. As it warms up a little hopefully I get to making a press and pucking die and try my hands at the wet “CIA” method

[@SnucklesX-9]

I think your channel is now reaching lab radar status now. Getting pretty deep on this, would like to see the farther distance numbers.

[@KevinSmith-yh6tl]

Great info. 👍

[@Everythingblackpowder]

Thank you

[@larryl43]

If I am not incorrect black powder does not completely burn. If I assume correctly the black powder gave the basic oomph and the smokeless bund itself plus the residual black powder. and as I am typing this your explanation does sound most plausible . THANK YOU

[@karlsailor]

I can heartily recommend a Garmin Xero chrono. Works great with rifle and handgun ammo.

[@ARandomTroll]

The "upside down" load actually matches my expectation. Black powder can get things moving but due to thermodynamics struggles to achieve high velocities (1800 fps is considered pretty good). Smokeless powder is mainly nitrocellulose which is not just more powerful but also produces lighter gasses which can push at higher velocities without loosing efficiency (556 does around 1 km/s, nearly twice that of BP, tank rounds get up to 1.6 km/s). The Idea is that the black powder quickly ignites while the smokeless powder sustains acceleration at the front of the gas column where it's lighter gasses are most needed. Sort of how you use solid rocket motors as boosters because they're cheap and powerful but thermodynamically lower efficiency. After the early phase of the launch you drop the boosters and continue with a hydrogen upper stage because it's a pain to handle but much more efficient, allowing much higher velocities. (orbital velocity is around 25000 fps+whatever you need to get up there) I love watching these sorts of weird tests.

[@wrsusinagem]

Smokeless powder is more sensitive to pressure, so igniting the bp first i believe is ideal.

[@G0ATLEG01]

I wonder if the increase in velocity is due to a more efficient burn. From what I understand black powder builds pressure immediately, where smokeless has a more slow and consistent burn. Thinking along these lines if the black powder is burning faster then it would make sense to capture the most of that energy first then let the smokeless powder burn through the rest of the barrel rather than having the slow burning powder ignite first and give it a kick of pressure somewhere a quarter or halfway through the barrel

[@wickdghost3639]

Try the faster burning powder on the top this time. Thats gotta give a little more. And i think it works that way because the black powder gets it movong then the smokeless gives ot that little extra nudge

[@jimv.661]

I could tell right away the upside-down load was faster because of the sound. I think the reason it is faster is sort of like a reburner on a wood stove, burning the extra gases that would normally go out the barrel.

[@GregClay-hr1qn]

Question, was the "upside down" as clean burning as the original? This is great stuff by the way. Keep on keepin' on!

[@Everythingblackpowder]

There was no noticeable difference in fouling between all these loads

[@mfree80286]

Wonder what mass fraction the BP solids form when they're propelled down the barrel. It's going to be a small number, but (and this is a serious "what if" speculation)... could SP-BP and mixed be suffering from having to accelerate the bullet *and* the residues, where BP-SP mostly propels the projectile, since the solids are mostly behind that charge? If you only had access to a high speed camera and some quartz tubes...

[@bakters]

Oh, it all makes sense, once I've seen the results! Obviously, I'd never guess it'd be like that beforehand... ;-) Anyway, it seems that smokeless being ignited late, once the pressure is already elevated by the burning black, that would make it burn faster. That'd create a higher pressure spike and flatten those primers. Reminder to myself: Don't *ever* mess with duplex loads!

[@weedwacker1716]

Congratulations on _science._

[@alexanderwilson527]

I suspect it is the greater heat of smokeless powder that makes it burn cleaner

[@wvcruffler123]

Just love to see that smelly belching out black powder. Smells better than cordite anyway.

[@Everythingblackpowder]

We think so

[@Aviator747a]

Everything I have seen before is the faster powder takes over and the slower powder acts like filler.

[@theThinkerator]

I remember reading about experiments by the ODGs where they duplexed and triplexed powders, AND mixed them Seems there is an application for all of them IIRC, the duplex/triplex loads had fast nitro powder farthest away from the primer, so as to burn only once in the barrel this helped accelerate the bullet once it was already moving by the slower powders I wonder how the BE would act not mixed, but put in last also, I wonder about $$, using a cheap surplus 50BMG powder, melt it in acetone, dry it, and grind it fine. this would remove any deterrent coating, and make it much faster, add this on top of slow/black powder

[@davidstuck2866]

Maybe I had it wrong all these years. But it was my understanding that duplex loads were SUPPOSED to be BP loaded first, then smokeless. And if there was much space left, some cream of wheat or poly fill on top of that. The idea being that BP is easier to ignite, faster burning (at least using rifle powder), then the smokeless burns better and more complete because of all of the HOT and burning BP igniting it. / I was also told that mixing the two together was NOT a good idea. Supposedly something about erratic burn speed and pressures. I guess that made a lot of sense to me because of the filler to keep the 2 powders from mixing.

[@noapologizes2018]

IMO, Stacking the smokeless powder on top of the black powder means it's the last to ignite. We are talking nano seconds here but my hypothesis is still viable. I'm guessing here, but perhaps that higher pressure at the end of the ignition may account for the extra velocity. Mixing on the other hand, dilutes the smokeless powder and affects the pressure created.

[@Everythingblackpowder]

Seems reasonable

[@herbertgearing1702]

This also makes me curious if you could achieve any benefit from doping a smokeless powder load with a small base of black powder or is it limited to cartridges which were originally black powder?

[@brianr555]

Looks like you have max’d out the 303 britt using the duplex “upside down”… mission accomplished?! Did you notice if all loads (mixed etc) were as clean? You metioned the extra pressure may have come from the bottleneck area in the round with the reversed duplx, will you be doing the same testing with the .45 colt? I just had to ask…another great video Jake! I learn in all your vids, thank you sir!!

[@Everythingblackpowder]

Thank you

[@frankkalisz7455]

Awesome! Do you have plans to do something similar with your 45Colt test loads?

[@frankkalisz7455]

Like many others I am astounded that the upside down load worked so well

[@Everythingblackpowder]

Yes I’m going to try the reverse powders charges and see it if gains velocity

[@buckstarchaser2376]

Now, you've got to try smokeless mixed, with some on top and bottom... just to be sure. Also, I'd like to see what would happen if you put ground up rice hulls that are coated in BP in the mix.

[@goiterlanternbase]

Cool that you tried😘 Now let me watch the video. 7:35 I knew it🤣🏆

[@jurah2o]

BP is exposive, Nitr0celulose is propelant and it mantains pressure until ball comes out. I think...

[@ryanb.9268]

It would have been interesting to see the faster smokeless on top of the black powder as well (not just mixed). Might actually get you to your goal.