Why does duplexing work?

[Limey]

When you shoot BP you get fouling......fact

To maintain best accuracy you must keep the fouling soft or remove it......fact

Modern BP burns drier than ''old time'' BP and therefore any fouling nowadays is harder......this what all the 'experts' say in their books

Adding a small percentage of smokeless powder as a ignition booster reduces fouling........again what all the 'experts' say in their books


OK, if modern BP burns drier than old time BP and leaves a harder fouling how does adding some even hotter and even drier burning smokeless powder make the hard fouling less or even non existant?


....for example,does the increase in pressure created by the booster charge of smokeless simply blow the fouling out of the barrel?

...but on the other hand, if the smokeless burns even hotter won't it just make the dry BP fouling even drier and therefore harder and even harder to remove?


.....what's going on here?????....I hope you boy's can explain the process to me.


....but accepting that duplexing does work, can you use the teensyist pinch of smokeless pistol powder.....say 3 or 4 grains?

.... or do you use just a tad more of smokeless rifle powder?....say 5 to 8 grains?


Safe shooting

Limey

[e15cap]

Don't know why it works, but, Harry Pope, thought so much of duplexing that he built a powder measure that concealed a smaller chamber inside. Moving the lever one direction dropped a measured charge of smokeless and the return stroke dropped the black. Crafty old divil, and one hell of a shot in his day. Best Roger

[jonk]

I suspect part of it too is quicker, cleaner, and hotter ignition.

[hyoder]

I would have to agree with jonk.

I have used 4759 in duplex loads for hunting loads in a 45-70. You can use up to about 10% 4759, i.e., if you use a 65 gr. charge of black you duplex would be 6.5 grs. 4759 and 58.5 grs. black. You should start with less that the 10% and see how much it takes to get a good clean burn - usually less that 10%.

[Boz330]

What I heard was that the smokeless adds more oxygen to the burn which helps comsume the fowling in the ignition process. It does work though.
Swiss powder seems to be more like the wetter powders of old. Of course without those powders to compare to, it is conjecture. It is most definately easier to clean up though.

Bob

[Don McDowell]

I've shot a couple of examples of the older black powder, lets just say that the glowing reports of how good it is, welll might be about as much wishful thinking as actual fact.
Duplexing was infact a good way to be able to better work with the black powder of old.
With todays black from all the manufactures' duplexing just flat isn't required.
Powders nowdays are as clean or cleaner, and just as accurate if not more so than anything that's been around in the past.
Primers are better quality, more uniform in burn, and non corrosive. That also leads to a difference between now and even back to the 1940's.
Duplex all you want, but as near as I can tell its a waste of perfectly good smokeless powder.

[DonH]

Don't know why it works, but, Harry Pope, thought so much of duplexing that he built a powder measure that concealed a smaller chamber inside. Moving the lever one direction dropped a measured charge of smokeless and the return stroke dropped the black. Crafty old divil, and one hell of a shot in his day. Best Roger

My understanding of Pope's duplexing is that he was using bulk smokeless for the main charge over a small "igniter" charge of black powder. The account I read of this (by which olrtimer I don't recall at the moment) said the bulk smokeless or semi-smokeless was harder to ignite. Better ignition = better accuracy, hence the BP igniter charge. Pope didn't want to "advertise" his secret so made up the tricky powder measure.

The club where I shoot BPCR allows duplexing and a number of shooters do so. I don't know that their loads are any more accurate than my straight BP loads but I can tell you they don't use blow tubes nor do they wipe barrels between shots or relays. I think it is a little chicken but to each his own, I guess. For what it is worth, a friend duplexes with BP; 4F kicker and Ctg main charge. His load shhots nearly as clean as the smokeless/BP loads and also w/o blowtubing or wiping the barrel. If I were going to shoot long range competition where duplexing is allowed, I might choose to use a smokeless kicker under the main BP charge in my .45-70 just to stretch it's legs a little. One gent who won LR at Raton a few years back said he used 5 grains of 4759 as a kicker to boost his .45-70 a little ways toward .45-90 perfoemance.

[Larry Gibson]

I mostly shoot duplex 45-70 cartridges in my TDs. Duplexing works very well, even with todays powders. I do not have to use a blow tube and I can shoot 100 round and have as little fouling as I have after 3 shots. Cant do that with straight black of any manufacture. Lots of theories as to why. Understanding that BP is primarily charcoal and that no matter how "hot" it burns the residue will be pretty much the same. Best explanation I've heard is that the column of pwder gasses of the smokeless powder is behind the column of BP gas and expells most of the bp gas in front of it out the muzzle. This makes the most sense to me. Especially since when working up the amount of smokeless to use you can actully see (with a bore mirror looking from the chamber end) the BP fouling progessively being blown out the muzzle end as one increases the smokeless charge. When all the fouling is blown out then there is really no need to further increase the amount of smokeless powder. The BP "fouling" is the long heavy dark black streaks of stuff you see, there will still be "normal" fouling from the lube etc..

Larry Gibson

[Limey]

....guy's this is all very interesting stuff...

.....even if nobody can say for definate how it works....but persaonaly I do go with the reasoning that the hot-poop booster smokeless powder literally flushes out the still burning BP so there is no chance for the fouling to deposit onto the bore.....

.....but the smokeless powder.....is it rifle or pistol grade?....is it fast medium or slow burning?

I am pretty limited on powder availability over here in France ....the local 'brew's' are made by Nobel.

I use Nobel Tubal 2000 in my smokeless 45 - 70 loads for hunting in my Marlin Guide Gun......for a 405 grain bullet you are looking at 45 grains as max loading.......our hunting is close range, between30 to 100 yards max so I download to 26 grains and pack out the space with firmly packed cotton wool.....works really well, bagged a 110kgs boar this January out around 100 yards, clean pass through, it was a running shot rear left hand hip in and front right hand shoulder exit.......no lack of power even with just 26 grains combined with home cast bullets made from wheel weights.

And I use Nobel Ba 9 in my 38 and 357 loads in my Python....with a 158 grain hard cast bullet 5 grains is considered a top end 38 load while 7.5 grains behind the same bullet is a top 357 load.

So anybody like to make some suggestions of which of these two to experiment duplexing with?.....I am not looking to gain any velocity....just make shooting and cleaning when using BP easier.

Safe shooting

Limey

[xtimberman]

Be careful. If you toss out that word, duplex, around some BPCR shooters, you'll be scolded and accused of heresy. This has always puzzled me, because late 19th century gun cranks discovered this trick as soon as bulk smokeless powders became available. That's over a hundred years ago, so cries of modern advantage ring hollow. I don't recall seeing Buffalo Bill's plastic blow tube at the museum at Cody. :-D

Harry Pope wasn't the only fellow who invented a duplex powder measure. Ideal offered at least two different models of duplex powder measures and many of their #6 measures are still in use by clandestine BP-duplex shooters.

Larry's explanation of increasing the smokeless component until the fouling is gone - then stop - is right on. Old timers would lay out old white bedsheets in front of the firing line when working up the smokeless amount. After each shot they would examine the bore and count granules of burnt black powder on the sheets to gauge if an increase or decrease of smokeless was in order.

I'd like to see pressure data comparisons on some duplex loads w/10% smokeless priming charge vs. 100% BP. Increases to much more that 10% by volume might be treading onto dangerous ground for some antique guns and certain action-types. This may be the main factor for many of the objections to these loads in BPCR matches.

SR-4759 seems to be the standard gunpowder for priming charges. I've heard of other smokeless powders being used, but I'd be afraid to experiment. Limey, I've never heard of any of those Nobel powders being used in duplex loads with BP.

xtm

[405]

I too have heard and read of others using all manner of smokeless types in their duplex loads. The pressure unknowns may get a little out of my comfort zone venturing too far off published/ pressure tested loads.

Limey,
I too don't have a reference for your powders but the two very commonly used smokeless powders for duplex loads are SR4759 and Accurate5744. They are both mid-fast powders that are very bulky. On a powder burn chart like that shown in the VihtaVuori manual these two powders are in the burn rate range of VhtV. N110, Norma 200 and RWS P806 and RWS R910..... if that helps.

Matthews stated that the pressure equivalent between smokeless and black in these type applications is about 1:3.... meaning the pressure generated by each grain weight of smokeless is about the pressure equivalent of 3 grain weight of black. How accurate that is I don't know but something to think about with duplexing.

Proceed with caution.

[Larry Gibson]

Limey

Sorry I can't help with Nobel powders as I don't use them. I've tried several different types of powders but pretty much prefer 4759. Keep in mind I use the duplex in trapdoor M1873s and there replica's. Some out there duplex to increase the power, I don't I only duplex to reduce the fouling and it does that nicely. In the 45-70 I reduce the BP 2.6 gr for every grain of 4759. My service load with a 500 gr bullet is 7 gr 4759 under 52 gr GOEX Cartridge. the velocity is equal to a straight 70 gr charge of COEX Cartridge with that same bullet. Some seem to like RL7 also but i've not tried it.

Larry Gibson

[Larry Gibson]

xtimberman

"I'd like to see pressure data comparisons on some duplex loads w/10% smokeless priming charge vs. 100% BP. Increases to much more that 10% by volume might be treading onto dangerous ground for some antique guns and certain action-types. This may be the main factor for many of the objections to these loads in BPCR matches."

As I mentioned in my post to Limey I reduce the amount of BP a a proportional amount to the 4759 I use. I have one of my trapdoors and a Siamese Mauser that is a 45-70 with strain guages on them so I may measure pressure using an Oehler M43 Personal Ballistics Laboratory. I jsut have gotten around to testing anything in those two rifles yet. I will be testing my own BP and duplex loads in the TD. I suppose I could load some of the 10% vs 100% duplex charges you mention and test them in the Siamese mauser. It will handlle the pressure. Any specific powder combinations?

Larry Gibson

[w30wcf]

I'd like to see pressure data comparisons on some duplex loads w/10% smokeless priming charge vs. 100% BP. Increases to much more that 10% by volume might be treading onto dangerous ground for some antique guns and certain action-types. This may be the main factor for many of the objections to these loads in BPCR matches.

The Lyman Cast Bullet Handbook shows this data:
.45-70 - 420 gr. bullet
7 grs. 4759 + 63 grs. FFG = 1,388 f.p.s. / 18,700 C.U.P.
.......................70 grs. FFG = 1,268 f.p.s. / 16,400 C.U.P.

Personally, when adding 10% 4759, I like to reduce the b.p. charge by 20% to equal the velocity of a straight b.p. charge.

w30wcf

[xtimberman]

Thanks Larry and w30wcf.

I don't have a .45-70, but my SR-4759/BP proportions are nearly the same for my 40-70 Ballard. The 2300CUP pressure increase from pure BP to the Duplex load are very comforting. I knew that the duplex load was almost certain to be of higher pressure - and I had hoped that the probable pressure increase wouldn't be excessive.

My Lyman Cast Bullet Handbooks have no duplex loads published in them, but they are old editions. Does the new edition have pressure data for duplex loads in other cartridges?

Larry, when you get around to doing your pressure testing, you might try to duplicate the Lyman pressure data that w30wcf noted - 7gr. SR4759+63gr. FFG and 70gr. FFG. It couldn't hurt to doublecheck Lyman's credibility.

xtm

[WickedGoodOutdoors]

This is the first that I have ever heard of Duplex. I have been shooting my TC .50 Cal Hawkins for over 30 yrs just using regular old FF Black Powder. Recently I have been using Pyrodex becuse finding Black Power is getting difficult.


How would you rig up to use smokeless? Maybe make a tissue paper cartidge like they used in Cival War rifles? with yhe two powders and the shot?

[SharpsShooter]

This is the first that I have ever heard of Duplex. I have been shooting my TC .50 Cal Hawkins for over 30 yrs just using regular old FF Black Powder. Recently I have been using Pyrodex becuse finding Black Power is getting difficult.


How would you rig up to use smokeless? Maybe make a tissue paper cartidge like they used in Cival War rifles? with yhe two powders and the shot?

This is for cartridge firearms loading, not front stuffers. I cannot recall ever hearing of duplexing in the muzzleloader.

SS

[xtimberman]

Amazing. Sometimes, I think that there's too much information floating around out there.

I'm glad SharpShooter straightened all that out.

Every so often, I read or hear about shooters duplexing loads in their C&B revolvers and MLs - and it almost always ends badly. A casual acquaintance was doing this very thing ~25 years ago with his TC Seneca to try to reduce fouling. I wasn't present when it happened, but his duplex charge blew the nipple out of the breech, bent the nose of the hammer and dug a deep 1/4" groove in his scalp from the eyebrow to the part in his hair. He was very fortunate. I saw some fellows looking at his blood all over the shooting bench the next day.

xtm

[montana_charlie]

....guy's this is all very interesting stuff...
.....but the smokeless powder.....is it rifle or pistol grade?....is it fast medium or slow burning?

So anybody like to make some suggestions of which of these two to experiment duplexing with?
Limey,
Here is some data from the DuPont site to start your thinking process...

SR 4759
This bulky handgun powder works great in the magnums, but really shines as a reduced load propellant for rifle cartridges. It's large grain size gives good loading density for reduced loads, enhancing velocity uniformity.

Taking that as a starting point, it appears that your Nobel Ba 9 is similar to SR-4759.

I used to keep some 4759 around (years ago), but I think I used it in shotgun shells...maybe.
CM

[xtimberman]

I used to keep some 4759 around (years ago), but I think I used it in shotgun shells...maybe.
CM

SR-4756 is a great shotgun powder. I can't recall any shotgun applications for SR-4759. Totally different.

xtm

[Larry Gibson]

.........Larry, when you get around to doing your pressure testing, you might try to duplicate the Lyman pressure data that w30wcf noted - 7gr. SR4759+63gr. FFG and 70gr. FFG. It couldn't hurt to doublecheck Lyman's credibility.xtm

xtimberman

Can definately give that a try. I 'm thinking of trying my load of 7/52 gr, wcfs mentioned 7/63 and then 7/70 as that would actually be a 10/100% load. I can shoot a string of 70 gr GOEX Cartridge to set a "baseline" first. What do you think?

Larry Gibson

[Ricochet]

The only duplexing in muzzleloaders I've seen "officially" recommended is for flintlocks using modern "replica blackpowders" to use a small priming charge of real BP with the newfangled stuff on top. I've never tried it.

[montana_charlie]

SR-4756 is a great shotgun powder. I can't recall any shotgun applications for SR-4759. Totally different.

xtm
As I said, it was long ago.
But the SR-4759 information from the DuPont site is valid.
CM

[Irascible]

Hmm, If our club puts on a BPCR match, how would one know whether a shooter was duplexing or not? For that matter how would one tell whether it was Triple 7 or American Pioneer?

[montana_charlie]

Hmm, If our club puts on a BPCR match, how would one know whether a shooter was duplexing or not?
For a match where ammunition components are restricted to specified choices, there is usually a provision for disassembling a randomly selected loaded round.
CM

[Don McDowell]

Hmm, If our club puts on a BPCR match, how would one know whether a shooter was duplexing or not? For that matter how would one tell whether it was Triple 7 or American Pioneer?

777 and app both put out a huge amount of white smoke, but no smell. So if somebodies smokin the place out, but there's no burnt bp smell .......
Also they'll likely be the ones with the lowest scores.:mrgreen:

[Ricochet]

Only "replica blackpowder" I've tried is Pyrodex. It makes a bit less smoke and smells WAY different from BP.

[Dale53]

The Canadian long range single shot competitions allow up to 25% duplex. Before the local BPCR matches went to NRA (Silhouette requires pure black or approved black substitute) we ALL duplexed. Most of us used 10% duplex. My favorite powder was RL-7 for duplexing (measured MUCH better than 4759 which measures poorly) and RL-7 is also some slower than 4759. I have shot thousands of these loads and they are a pleasure to shoot. Shoot all day without that DERN blow tube without fouling problems. For the record, I shot 10% smokeless.

Pat and Spence Wolfe's book on the trapdoor stated that each grain of smokeless was worth about 3 grs of black powder. So, you will get a small increase in pressure and velocity but according to Lyman's pressure testing information, well within the limits of a Trapdoor Springfield.

Dale53

[Boz330]

Limey

Sorry I can't help with Nobel powders as I don't use them. I've tried several different types of powders but pretty much prefer 4759. Keep in mind I use the duplex in trapdoor M1873s and there replica's. Some out there duplex to increase the power, I don't I only duplex to reduce the fouling and it does that nicely. In the 45-70 I reduce the BP 2.6 gr for every grain of 4759. My service load with a 500 gr bullet is 7 gr 4759 under 52 gr GOEX Cartridge. the velocity is equal to a straight 70 gr charge of COEX Cartridge with that same bullet. Some seem to like RL7 also but i've not tried it.

Larry Gibson

I use to use the RL7 in my 40-65 when I first got it and it worked well. I don't remember the exact load but the load came with the gun as a suggested load. It did give about 100fps extra velocity over a straight BP load.

Bob

[iowa]

The NRA produced a "white paper" on duplexing some years back. I'm sure it's out there somewhere, and I'd like to re-read it again if someone can find it. From what I recall, and don't count on this as gospel, I think the bottom line was stay at 10% or less for safety and reduce your BP volume an equivelent amount.

[NavyVet1959]

I have one of my trapdoors and a Siamese Mauser that is a 45-70 with strain guages on them so I may measure pressure using an Oehler M43 Personal Ballistics Laboratory. I jsut have gotten around to testing anything in those two rifles yet. I will be testing my own BP and duplex loads in the TD. I suppose I could load some of the 10% vs 100% duplex charges you mention and test them in the Siamese mauser. It will handlle the pressure. Any specific powder combinations?

It might be interesting to compare the typical duplex of a fast powder under a slow powder with a case of that fast powder being thoroughly mixed with the slow powder to see what sort of differences in speed and pressure was generated.

[Oyeboten]

When you shoot BP you get fouling......fact

To maintain best accuracy you must keep the fouling soft or remove it......fact

Modern BP burns drier than ''old time'' BP and therefore any fouling nowadays is harder......this what all the 'experts' say in their books

Adding a small percentage of smokeless powder as a ignition booster reduces fouling........again what all the 'experts' say in their books


OK, if modern BP burns drier than old time BP and leaves a harder fouling how does adding some even hotter and even drier burning smokeless powder make the hard fouling less or even non existant?


....for example,does the increase in pressure created by the booster charge of smokeless simply blow the fouling out of the barrel?

...but on the other hand, if the smokeless burns even hotter won't it just make the dry BP fouling even drier and therefore harder and even harder to remove?


.....what's going on here?????....I hope you boy's can explain the process to me.


....but accepting that duplexing does work, can you use the teensyist pinch of smokeless pistol powder.....say 3 or 4 grains?

.... or do you use just a tad more of smokeless rifle powder?....say 5 to 8 grains?


Safe shooting

Limey


I have eliminated all fouling of any consequence with the use of simple Bees Wax empregnated Wafers, cut from ordinary white Paper Towel.

The Wafers are very thin and do not displace enough Powder to matter.

I simply run torn one inch or so strips of white Paper Towel, through a little Pan of Molten Bees Wax, and once cool, I cut the Wafers out, using a Hollow Leather Punch or Gasket Punch.

For me this is with .44 Cap & Ball Revolver, or for Metallic Cartridge Black Powder Revolver in .45 Colt and also .38 Special.

I have fired several hundred rounds over a few months in my UBERTI Walker, with no cleaning of any kind, and with no fouling that is even worth mentioning...and also I have had no rust whatever with it sitting around uncleaned.

All I end up with is a little bit of light, soft, greyish film, which offers no drag at all to the rotation of the Cylinder, ( Cylinder to Forcing Cone gap is about .002 ) and whatever light soft 'film' is in the Bore, it comes out super easy with a Nylon Brush and some warm soapy Water.

Simple...easy...fun...and works splendidly.

If in a Hot clime ( as I was, in Las Vegas, ) one can add some Caranuba wax to the Bees Wax so the Wafers do not stick to gether so much in the field.

I make the Wafer with a Gasket Punch over smooth End Grain of Pine...and I make them to be a little larger than the Bore diameter, so they fit snug in the Cartridge or the Cylinder or the Bore, as may be.

This was with "Goex", so, if anything, it will work even better with a less dirty Powder like "Swiss".


"DUPLEX" wise, my own experiments have been limited to .38 Special using present day run of the mill Cartridge cases.

This was about six years ago or so and my Notes are not handy, but...

What I did was to use a small percent by weight less BP, and then added that same percent by weight of "UNIQUE".

I forget now how high up I went percentage wise, but I think the highest I did go, was still fairly low, like maybe 3 percent, tops...and in 1/2 Grain increments.

Anyway, as I went though so many rounds of just 18.5 Grains of 3 F Goex by itself, then to one Grain UNIQUE and 17.5 Grains of Goex...to 1 1/2 Grains UNIQUE and 17 Grains GOEX, then 2 Grains Unique, 16.5 Goex, etc...

Chronograph results were entirely progressive and stepped evenly.

This can allow one to have a little extra zing with an erstwhile BP metallic Cartridge, within whatever limits one feel sure are still safe & sane for the Arm in question.

It worked perfectly, and no surprises or funny results...each round was dead even and did as expected to within a few FPS and no deviations beyond what would have been normal anyway.

I had the UNIQUE mixed as evenly as possible in the BP with mine.

I used UNIQUE because I only had it or Bullseye on hand to do this with.

No doubt other Smokeless Powders would give slightly differing results.

[johnson1942]

j duplexed my 45/70 untill i discovered blackhorn 209 powder. now i use it in both my 45.70/s, my 4 cowboy revolvers,and all my muzzleloaders useing a magspark nipple. duplexing works but why do that when you can use blackhorn 209 powder. a shooter called me from the east coast once and said a lot of flint shooters use a little 3f real black in their flinters out their with the main charge of 209 powder. no fouling at all. i also used reloader 7 in my 45/70 and it shot great but the recoil was more than i liked so i went back to blackhorn 209 powder.

[.22-10-45]

Working with an original Ballard in .25-25 Stevens. Using Swiss 3Fg, I tried SR4759 up to 3.0grs...didn't really clean up anything. Went to 2 -3.0grs. PB..bore looked like a clean burning smokeless load had been fired. When shooting straight Swiss, I could blow tube between shots & get 1" accuracy at 50yds..probably good enough for hunting, but for match accuracy, 1 barely damp patch thru & bore left damp, produced 3/8" groups at 50yds. With the PB duplex, I still had to patch thru after each shot to equal best black accuracy..however, I now only needed 1 dry patch thru. I figured if I still needed to patch, might as well use a barely damp one & use straight black..MUCH less headache if loads ever needed to be pulled! I was using SPG on an original Ideal .25 100gr. 20-1 lead/tin bullet.

[RPRNY]

It "works" only by increasing the combustion of BP residue that would not otherwise have been combusted, thereby diminishing the amount of visible reside, but, I see no reason not to join you in the supposition that it may also increase the hardness of remaining residue. I do not duplex any BP loads anymore. Soft residue is easy to deal with.

[EDG]

The physics of chemical reactions that you are exposed to in college chemistry explain that any reaction happens faster at higher temperatures.

The SR4759 duplex loads will generate higher pressures faster than a straight BP load and consume the charcoal part of the mixture more completely.

SR4759 is also known for leaving zombies (large unburned grains of powder at low pressures) in the bore when loaded straight with no BP. When you increase the load a grain or two, instead of getting more zombies, you get less zombies as the pressure goes up.

[Ballistics in Scotland]

The only duplexing in muzzleloaders I've seen "officially" recommended is for flintlocks using modern "replica blackpowders" to use a small priming charge of real BP with the newfangled stuff on top. I've never tried it.

This may well be safe - I don't know for sure. But duplexing a muzzle loader with conventional smokeless powder and a larger charge of black is really, seriously dangerous. The main reason is that the confinement of the smokeless powder is likely to be inconsistent.

I had an interesting experience many years ago, with the Portuguese 8x60R. I had worked out a Reloder 7 load which was very reassuring on pressure indications, but came nowhere near filling the case, and would be liable to inconsistent if it got to lie in different positions. So I did the very opposite of duplexing. I topped it up with Nobel black powder, which in those far-off days was of rather poor quality. I could see no way the combination could give excessive pressure, and neither it did, insofar as it was judgable by the case and primer.

What happened, though, was that the case necks were wrenched off and carried down-range. I never, unfortunately, recovered the bullets, but imagine they remained attached. I see this as similar to an experiment by Dr. Franklin Mann, who wanted to investigate the effect of a full or non-full case without altering the charge. It seemed natural to use an inert powder, and he (presumably with a barrel at the end of its life) used sand. It apparently locked togelither, and into the case neck, like my black powder did.

[RPRNY]

What happened, though, was that the case necks were wrenched off and carried down-range. I never, unfortunately, recovered the bullets, but imagine they remained attached.

Sounds like it may have been a slightly sobering moment. Glad it was an easy lesson and not a hard one. As you say, intuitively nothing there to give serious pause. I wonder what would have happened with the BP loaded first and the RL7 on top? The BP certainly would have ignited, as would the RL7. Whether there would have been a pressure spike or not is hard to say.

[BrentD]

I have shot duplex loads, briefly. I did it early on in my experiences with BPCRs. It worked after a fashion, but it hit me one day that shooting duplex was destroying the things I liked best about bp. Namely the traditional authenticity of using straight black and then (and more importantly) the challenge of shooting straight black. If I didn't like the challenge (some consider a hassle) of black powder then why shoot any at all? Why not shoot just smokeless? As soon as I realized this for myself, I never shot another, and never will. There is just no need for me to go there, and every reason not to.

[Hiwall55]

I use RL-7 in my one duplex load, I shoot one match where you have 11 shots in 5 minutes at different yardages with no spotters. No time to blow tube or wipe. 6 gr. RL 7 and 58 grains of FFG

[Ballistics in Scotland]

Sounds like it may have been a slightly sobering moment. Glad it was an easy lesson and not a hard one. As you say, intuitively nothing there to give serious pause. I wonder what would have happened with the BP loaded first and the RL7 on top? The BP certainly would have ignited, as would the RL7. Whether there would have been a pressure spike or not is hard to say.

Appearances notwithstanding, I was sober to begin with. It happened with 100% of two cases before I noticed, and I declined to find out whether that was a statistical anomaly. As to pressure, the indications were that it behaved exactly as I expected, a slight but entirely acceptable increase over the smokeless alone. But I don't intend ever to find out whether that was consistent, or what happens with the same constituents in reverse order as you suggest... I'm sorry, no insult intended. I should have said "as you speculate on".

I don't know whether this event depended on the rather poor quality of the powder, which users of the time called "nutty slack", a term traditional to the British coal merchant. It gave about 1300ft./sec. in that rifle, when the original, filling a slightly thinner case, gave 1700. I regularly used 5gr. of fast-burning smokeless under a full case of that black powder, though, with no ill effects at all. The worst that can do is nothing at all, and I know it reduced fouling in my particular case.

I used to spend a lot of time in Arabia looking at sand, which is extremely idiosyncratic stuff, and reflecting on Major Bagnold, who served in the First World War, pioneered motorized desert exploration in Model A Fords, and became a consultant to NASA on the sands of Mars. The different sides of wind-blown ripples have different colours, and the second person or vehicle can sink into sand the first has barely imprinted. Dry, fluid sand will stop a bullet in a shorter distance than damp. Similarly, fractured rice grains used as wadding in a shotgun can give abnormally high pressures. What matters to us is that any hard, granular substance which doesn't ignite, can apparently lock together under sudden impact.

It is hard to know how people can accurately compare current and earlier black powders, and I am unconvinced as to improvements, as long as we are comparing like with like. Military powders were an important - even the - war material, produced in great quantities. British law and other people's judgment forbade the incorporation of more than 60lb. in one batch, so the incorporating time was the minimum that would do a satisfactory job. I doubt, though, whether we have achieved superiority over the best sporting and target powders as they left the factory.

[Bent Ramrod]

There's a sort of "Laffer Curve" relating to shooting vs. cleaning in relation to bore size, at least for most people. Except for 3-1/4" cartridges, and maybe the .40-90 bottleneck, fouling can be "managed" short of cleaning the bore between shots, down to .38 caliber, for target accuracy. The .38-55 comes under this management scheme because of the relatively light powder charge. The "management" consists of proper loads and lubes, blow-tubing, etc. In this area of the curve, the shooter does more shooting than cleaning.

For anything below .38 caliber, and for those heavily charged .38s like the .38-72, most people are doing more cleaning than shooting in a typical extended black powder shooting session. I can blow tube my black powder .38-55s, but down at .32 caliber, whatever the BP charge, I duplex in order to shoot. SR-4759 is thee duplexing powder for me; I tried Bulk Shotgun and some of the flake stuff and nothing else worked as well.

The .32 calibers were on the edge of practicality in the black powder days, and "The .25 Caliber" (i.e., the .25-20SS) was written up in the shooting literature as the latest exciting development. It was conceived as a hunting cartridge, though, and not as something to be fired in long strings without cleaning. There was also a development which was probably similar to the .25-35, which the inventor acknowledged was only for the crankiest of gun cranks, as any normal shooter would find it impossible to get working.

Many of the scores and groups sent in to the periodicals of the day, now commonly assumed to be black powder loadings, were made with King's Semi-Smokeless powder, which may have engendered the idea of duplexing black powder. Semi-Smokeless was an incorporation of black powder and nitrated wood pulp or cotton linters. It was not without its hazards, but the user could shoot all day without cleaning or wiping. The extra gases from the combustion helped sweep the solid combustion products of black powder (about 55% of the total) out of the barrel.

[Ballistics in Scotland]

Henry Melville Pope built rifles in .25 and .28 caliber which were, for several decades, the most accurate in Creation. But they are the exception which proves your rule. Initially these calibres were probably used in target shooting disciplines which permitted very frequent cleaning, and the same applies to people who only want to eat a rabbit or two a day, or rid the farm of a woodchuck or two. Even the black powder .22WCF worked well for that. Late Pope rifles, to get away with such small bores, had Metford-style segmental rifling and used his system of breech-loaded case and muzzle-loaded bullet from a false muzzle.

Pope claimed that finning at the rear of the lands was inevitable when the bullet was breech-loaded. I'm not so sure that it is, and a gas-check or discarding card wad and'or wax cookie would surely put this right. I think the main advantage was that the muzzle-loaded bullet wiped much of the fouling away on its way down.

[doc1876]

Ok, while we are at it, what about compression?
I compress my BP loads a little over 1/8 inch. How about duplex? I have heard from none, to a little.

[Bent Ramrod]

I don't compress my .32-35 or .32-40 loads, which so far are the only ones I've duplexed on a routine basis. I use Swiss powder in these, which generally doesn't need compression.

[BrentD]

why do you duplex those cartridges instead of shooting straight smokeless?

[Bent Ramrod]

Brent,

I shoot straight smokeless in my High Wall .32-40, but the "other" .32-40 is a Stevens 44 and the .32-35 is a Stevens 107 (same action), so I prefer to keep the pressures low. Also, I sort of like "kickin' it Old School." It's interesting to see how things were done in the old days.

[BrentD]

I'd not be so sure that duplex is that low pressure. Several folks have discussed pressure "excursions" in duplex loads. As for "kickin' it old school" that would be doing it with straight black. Duplexing pretty much eliminates the challenge of using blackpowder.

[Bent Ramrod]

I see no pressure excursions in my own loadings, and nobody seems to have reported them in Shooting and Fishing back in the old days. They were pretty good about reporting firearm accidents as object lessons for the subscribers. Blown-up guns back then were typically Damascus barreled shotguns overloaded with smokeless powder by the careless and uninformed. I would not be surprised if that was the root of most of the same problems reported today. Those following the loadings in the back of Ned Roberts' Match Rifle book are asking for pressure excursions for sure; as someone wrote in the margins of my copy, "Every load in here is too d__n HOT!"

King's Semi-Smokeless hit the market in 1896, and was immediately popular, which is "Old School" enough for me in the small bore cartridges. As I mentioned, the larger bores and more lightly charged medium bores with straight black powder offer enough challenge to be fun and still get some shooting done. The bench rest black powder rifles of that time were mostly .38-55s; the .32-40 became popular in offhand shooting for the lack of recoil, a factor in a 50- or 100-shot match. With King's Semi-Smokeless and the practice of duplexing, scores improved. The "remarkable accuracy" of the .25-20 Single Shot in its black powder loading was about 2" at 50 yards. However marvelous it was back then, I want more.

I guess it just depends on how much Authenticity one can stand. I used to know a bunch of people in the Society For Creative Anachronism. They made elaborate costumes, held feasts and swordfights, and strove for the authentic experience of living in the Middle Ages. I told them they weren't all that Authentic because back then everybody had fleas. That level of Authenticity they didn't want.

One thing that really struck me in my reading of Shooting and Fishing was that those people did not have a nostalgic bone in their bodies. Everyone was "up to the minute." The last thing anyone wanted to be was a "back number." So within that context, a nostalgia factor in the present time for duplex loading is legitimate. I hear people are getting good results with Blackhorn 209, and good for them. If they want to revel in technological progress, it's fine with me. In that context, I'll remain a "back number," and wonder why they don't handle the challenges of duplexing.

Steve Garbe shoots black powder in Scheutzen matches. I don't know what caliber he uses or what he does about bore cleaning, but obviously he does very well. A Schuetzen match is supposed to be a pretty leisurely affair, with plenty of time between shots. As Ballistics mentioned, loading from the muzzle might perform the bore mitigation by itself, and there would be time to do that.

Some people do very well on or over the edge of practicality, but most do not. A friend of mine, in the midst of severe rotator cuff problems, spent about $2000 on the advice of a prominent engineer and experimenter who claimed that a heavily charged .38 caliber offered accuracy, ease of operation, and all the power a silhouette shooter would need without the recoil of the bigger bores. He rebarreled and rechambered one of his rifles to the engineer's specifications, got reloading dies, shells and the recommended bullet moulds. Following the engineer's directions, he couldn't get his outfit to shoot, and called him for advice, getting nothing but a lot of rude language for his troubles. I noticed later that the engineer was offering barrels and tools for that caliber for sale; maybe he couldn't get it to work in the long run, either.

I remember a visiting professor telling us in the course of a lecture that part of being a scientific genius is knowing which problems are worth the effort of solving. That's an individual decision to make.

[BrentD]

A lot of us have .38 caliber rifles that don't shoot well and were built to the specs of an "engineer". I have one myself. I know something about the language issues as well. 'nuff said of that. :(

As for shooting black in matches, lots of us do it. Myself included. The challenge of shooting black is lost when duplexing is included, but with straight black the games are more interesting to me. It's not even close to the edge of practicality - when you figure it out.

Lots of folks never had any problems with pressure excursions or other untoward events - until we did. Then a gun that was always safe before, suddenly blows up with a load that had been shot in it many times previously. Don't ask how I know...

[Gunlaker]

I tried a little duplexing when I first started shooting these rifles, but like Brent, I prefer to use straight black. Pretty much for the same reasons.

Bent Ramrod you make a good point regarding the old timers being much like most modern shooters in that they really wanted to be at the forefront of technological advances. We BPCR people have more or less frozen our technology to a specific time.

As far as I remember, from reading the BPCR News, Steve Garbe shot 38-50's and .38-55's when shooting from the bench, and managed fouling by blowtubing and following with a dry patch. I've heard of very few others trying that technique.

Interestingly I find that my .32-40's and .38-55's foul less than my .45-90's do when shot with straight black. Mine are shot breech seated so charge weights are quite high. I use 45gr or so in the .32-40, and sometimes as much as 59gr in the .38-55. My easiest to clean BP rifle is a .32-40 with a 25 year old Ron Smith barrel on it. This might be because the barrel is very smooth inside. One quite wet 2" Arsenal patch after each shot cleans it right out. I follow with a single lightly damp patch to keep the bore condition the same between shots.

I have a few .38-55's, but the most accurate one is a CPA that just has a standard SAMMI chamber cut into it. It was supposed to be a long gentle throat but got cut with the wrong reamer.

Chris.

[Lead pot]

I shot three duplexed ladder loads a couple years ago to give it a try. I had the chronographs set up to see what the loads where doing. The ladder loads where three rounds each from zero compression to I think .350" and the ES I saw shot with the three ladder loads convinced me to stay with straight Black.

Chris I used to blow tube and run a dry patch it worked ok but using the wet and dry patch is much faster when time counts.
When your shooting in temperatures during the hot summer, where the barrel gets so hot during the shots for score the wood forearm gets hot and the screws holding the forearm burn your hand the patches damp or wet come out steaming, the bore is dry before you get the next shot off. It don't matter if your shooting in all parts of the country, dry part or high humidity. Hot is hot :)

Kurt

[Regulator.]

interesting

[Gunlaker]

Kurt, I'm not 100% certain, but think a lot of those schuetzen matches had covered firing lines. I've never had a barrel get too hot to touch except when shooting out in the sun. I wouldn't be surprised if there are exceptions in cactus land though :-)

Chris.

[Lead pot]

Chris, the Schuetzen shooters don't use 90 to 105 grains like I use either. And your right about the covered lines shading the sun and keeping the barrel temps down.
This summer I again spent most of my time in Montana like I do yearly and it was hot. The Gong shoots where have you have 5 to 8 shooters on line and it moves fast, not like a long range type of match where you take a 1/2 hour to shoot your sighters and 10 for record. Your name is called and you should get the shot off with in reason. No waiting out condition change like a long range Creedmoor type match.
Even at Alliance Sagebrush match there is a part covered line and some tent cover and ten shots gets the barrel so hot you cant touch it getting off the ground.
The Mt. 1000 there where 6 on line and it moved fast. I pushed one damp patch followed by a dry and the damp patch came out steaming. I changed to a wet because the damp patch pushed through a little hard. The wet patch was steaming big time laying on the ground.
Naw there is a difference between the small calibers the Scheutzen guys use and what we use I the big bore rifles.

Are you coming to the Lodi long range match?

[johnson1942]

im only 60 miles from alliance, when do you shoot their, may visit.

[Lead pot]

http://alliancerifleclub.com/uploads/3/4/9/6/34961683/2016__hoffland__schedule.pdf

I will miss this fall shoot. Going to Alma MI. next week.

[Gunlaker]

Kurt I would like to go to the Lodi match one day, but not this year. My list of things to do is over full already for this year :-)

Chris.

[BrentD]

FWIW, and since this is about duplexing. The practice is allowed at Lodi, but ONLY for the Fall match. The spring long range and the summer midrange matches are NRA BPTR registered regionals and hence allow only straight black.

[country gent]

While i have not duplexed any of my BPCR rounds ( 38-55, 40-65, 45-70, and 45-90) Nor have I tried any smokless powder loads either. I have wondered if 5% or so of 3 or 4F powder in the bottom of the case with a appropriatly reduced main charge compressed to hold everything in place would help any? I blow tube mostly 1-3 long breaths with a swallow of water every couple shots to keep moisture levels up. I do clean between stages a brushing with windex vinegar or ballistol mixed 1 part balistol to 4 parts water. When I clean the brushing lossens what is there the first patch is black and very cruddy the second is dark grey with a few black streaks and the 3rd is pretty much clean with only a few light grey smears. I have wondered on the finer powder as a ignitor charge for several years but never tried it.

[Ballistics in Scotland]

I guess it just depends on how much Authenticity one can stand. I used to know a bunch of people in the Society For Creative Anachronism. They made elaborate costumes, held feasts and swordfights, and strove for the authentic experience of living in the Middle Ages. I told them they weren't all that Authentic because back then everybody had fleas. That level of Authenticity they didn't want.


In the 1970s I was introduced to, I suppose, the last Arabian Bedouin who had lived in the desert with no contact with modernity in any form. My translator told me one of them said it was the best life on earth, as long as "little curly thing on end of gut" doesn't go bad.

There is duplexing and duplexing. If you had only one entirely reliable size and shape of powder grain, and if your powder space extended to the end of the universe, the size of grain would make no difference to the ratio of powder to spaces in between the grain. If you had to put 1in. spheres in a cylinder 1.99in. long and 1.99in. wide, you would have a drastically reduced ratio of powder to empty space. Powder in a cartridge is somewhere between those extremes. But if you mix two sizes of powder, the small grains fill in the spaces between the large, not merely increasing the surface area the powder can burn on, but greatly increasing the loading density. This technique, sometimes used by intrepid experimenters with smokeless, can be very dangerous. While it can enhance performance, it needs to be professionally tested with the sort of equipment you don't hold against your cheek. I would want to mix the powders separately for each cartridge... No, that isn't strictly true. I wouldn't want to mix the powders.

It is a pity that people haven't employed a different word for the use of a little smokeless powder to enliven black. It needs to be very little, and a fast powder. The aim is to send hot gas among the black powder grains, to ensure good ignition and to raise the gas temperature = not to alter the burning rate or provide more power.

[Bent Ramrod]

You are absolutely right, Ballistics. Nobody has discussed actual duplex loading as it was practiced (and still is, putatively, by brave souls who would otherwise be walking tightropes between buildings or jumping motorcycles across the Grand Canyon) since my last post until yours. An old-time, large-bore, large-capacity case with a full nitro-for-black smokeless charge in it, followed by all the black powder the reloader can bootheel in there, is, technically, a "duplex" charge, and, no doubt, dangerous. The reloader who does this is, technically, an idiot, who deserves what he gets from this concoction. As does the guy who leaves air space in the shell so the ingredients can mix while the outfit is being transported to the range. Neither of these are examples of proper procedure.

A friend of mine bought a real nice 1892 Winchester one time, in .44-40. At the time, ammunition and shells for reloading were obsolete, and impossible to get through regular sources. A few Gun Shows later, he found a box of old .44-40 reloads, and we repaired to the desert to shoot the rifle for the first time.

The first shot made a kind of "thoooommp!!" sound, and when he opened the breech, the shell popped out like a champagne cork, followed by a mess of unburned powder and Cream of Wheat. The reloader, terminally unclear on the concept, had obviously read somewhere that small charges in big cases need a filler to hold the powder against the primer for best results. He put in enough filler to allow a nice dilution of the powder charge in the airspace he left in the cartridge. So the shooting session adjourned to get the stuck bullet out of the barrel, clean the debris out of the action, break down the reloads and load them properly (without filler). This could be taken as a dire warning against the use of fillers, anywhere, any time, but the warning we took from the episode was "Never shoot anybody else's reloads."

As I mentioned, the big calibers don't need duplexing, or much cleaning, as the fouling can be managed in other ways. That is why, in the black powder days, the bores started out at .75 caliber and slowly crept down to .50, and then to the revolutionary "small bore" .45 caliber, as basic understanding, lubricants, loadings and bullets got more sophisticated. In the smaller calibers, for those who don't like cleaning, duplexing, done the way Harry Pope and others did it, is fine and safe. And of historical interest, and, not without the internal rewards of continuing a tradition. Also, despite chronograph testing and whatever other proxies one uses, it might just provide better results on the actual target, if one cares to test in that way. It may even work on those oversize .38s; I guess we'll never know. My friend spent even more money getting the barrel rechambered to a smaller shell.

There used to be a concept called "risk management," where a process was analyzed and methods developed to make it safe, as long as those methods were adhered to. I don't know what happened to that; risks now seem to call for injunctions from authority figures only. It might be this Age of Litigation we are in; but I recommend nothing, just report what I do and what works for me.

I have noticed nobody, in the ASSRA match results, who shoots black powder in their small-caliber Scheutzen rifles, or duplex loads either, for that matter, so the "many" who do so are surprisingly invisible. The WSSM might do so, but I see no records set by them. Of course, they have no magazine, just a page in BPCR News, and their web site crashed a while back, so maybe I'm missing it.

Finally, with all due respect, I have to address this issue of "it works fine, and then, one day, KABOOM!" A rifle action that was recognized as problematic in the 1920s, was rotated out of military service (and civilian marksmanship, if the shooter sent his rifle in) throughout the 1930s, was checked again in the 1970s, with results that suggested that even those actions that passed muster 50 years previously might have gone on embrittling over the years until all of them were dangerous, is not exactly something that lets go without warning. In the job I used to have, all the energetic materials "incidents" seemed to come out of nowhere, at first. And then after the smoke cleared, the analysis would show that corners were cut, and gotten away with, and procedures were abbreviated, and gotten away with, and safety warnings were ignored, and gotten away with, and mix sizes were increased over limits, and gotten away with, until came the day when it was not gotten away with. I fully sympathized then, and do now, with the injured, but if you're going to be in the energetics business, or the antiques business, (in our hobby, it's both), it is often better to do your research beforehand than get the data directly. And I am no better than anyone else here; we are all one mistake away from humiliation or worse. The point is to always be careful. Enough said.

[BrentD]

Bent ramrod, you are entitled to your own opinions. My opinion, however, is that I don't agree with any of them in your last post.