A 'Savage' View of Duplexing Dismay

[RandyWakeman]

In a sport where many seemingly cannot decide whether to use Pyrodex RS vs. Select or "P," or Triple 7 FFg vs. Triple 7 FFFg-- that last complication a new shooter needs is to decide is which two smokeless powders he should combine. According to every major powder manufacturer I've discussed this with, results are unpredictable-- unapproved, untested, and fundamentally unsafe. Neither SAAMI nor the CIP allow any such combinations of dissimilar powders in any small arms application. Smokeless powder can vary from lot-to-lot, the amount of variance when attempting to combine powders introduces the possibility of far more uncontrolled anomalies.

Some of the common ballistic laboratory tests that can be used to determine the viability of a new propellant in a confined space include:

Minimum Explosible Concentration (Bureau of Mines 20-Liter Chamber) ASTM E 1515
Pressure, Rate of Pressure Rise and Explosion Severity (Bureau of Mines 20-Liter Chamber) ASTM E 1226
Pressure and Rate of Pressure Rise (1.2-Liter Hartmann Chamber) ASTM E 789
Minimum Autoignition Temperature (Dust cloud) (1.2-Liter Furnace) ASTM E 1491
Minimum Hot Surface Ignition Temperature Bureau of Mines Procedure
Concentration Limits of Flammability ASTM E 681 and ASTM E 918
Temperature Limits of Flammability ASTM E 1232
Minimum Ignition Energy and Quenching Distance ASTM E 582
Autoignition Temperature ASTM E 659 and ASTM G 72
Open Cup Flash Point and Fire Point ASTM D 1310
Closed Cup Flash Point ASTM E 502
Substained Burning ASTM
Relative Quickness (Closed Bomb, Pressure Time) MIL-STD Method 801.1
Detonation TB 700-2 and UN ST/SG/AC.10/11/Rev.2
Koenen UN ST/SG/AC.10/11/Rev.2
Gap UN ST/SG/AC.10/11/Rev.2

This is quite far from a comprehensive listing.

"Duplex" loads are a peculiar notion that I'm personally completely against. They are not allowed by Savage Arms, not laboratory tested, nor are they allowed by any major smokeless powder manufacturer that I'm aware of. No reloading manual suggests their use under any circumstances; most loudly caution against ANY comingling of powders. I wish that those that fancy themselves as experienced reloaders would take a deep breath, step back, and count the number of "duplex" powder loads they use in firearms other than the Savage 10ML-II.

When unknown levels of heat and pressure are introduced, the resultant metal fatigue and erosion over time also becomes an unknown quantity. There are several considerations there, as well, as noted by the US Navy Gunnery Dept.:

Gun barrel fatigue process

a. Heat checks

(1) Also known as crack initiation.

(2) Small (sometimes invisible to the naked eye) cracks in the surface of the bore.

(3) They can reach an approximate depth of .005" to .025".

(4) May also start to occur after firing approximately 300 rounds.

b. Slow crack growth

(1) Once the heat checks/cracks are formed, these cracks continue to grow slowly under the influence of stress in the gun barrel wall arising from the pressure versus time history during firing.

(2) At this stage the heat check/crack will appear in a checking pattern and will be deeper than .025".

(3) Heat checks/cracks will then connect together to form longitudinal and circumference cracks.

(4) Longitudinal cracks which are long and continuous and reach a length of approximately 2.5" to 3" will result in the condemning of the gun barrel.

(5) Circumference cracks which extend approximately one of third the inside circumference of the gun barrel are justification for condemning the gun barrel.

c. Fast crack fracture

(1) When the crack grows at a very rapid rate (which can reach 5000 ft per sec) a condition known as fast fracture is reached. This condition produces catastrophic failure of the gun barrel structure

d. Gas washes

(1) Also known as flame washes

(2) Generally occur near the origin of the bore

(3) Steel in the barrel physically melts away.

(4) Caused by hot high velocity gases

e. Gas pockets

(1) Concentrated area of gas washes

(2) Melting of the gun barrel interior surface causing imperfections

(3) Gas pockets which obtain a depth of .100" constitute criteria for regunning.

As it is, with N110 or similar, all the gas needed to destroy accuracy is available to the new Savage shooter, with as much recoil as most care to enjoy. The Savage 10ML-II is such a clean, simple, safe gun. To throw that away with homebrew mish-mash duplex / triplex loads has no merit. Not one firearm I have ever owned, rifle, pistol, shotgun . . . has ever performed at its best with the fastest thing that comes out of the muzzle. The 10ML is no exception. There must be something about the human condition that compels us to abuse our equipment?

Already, there are well-proven, accurate 2300 fps arena loads with Vihtavouri N110 and other straight powders that retain plenty of energy to cleanly harvest any deer on the planet to 500 yards, and are easy 230 yard + MPBR loadings. The last thing needed (IMO)  is an extra 200 fps with loads of unknown pressure, and to promulgate duplex loadings to a prospective new Savage owner is a bit negligent, in my view. As a matter of course, as muzzle velocity increases, the BC's diminish in concert. At range, game-harvesting effectiveness differences for North American game animals is little more than trivia.

All this, in a sport where sub-100 yard hunting is the norm, and sub-50 yard shots the most common whether ML or center-fire. I believe that to continue along these lines is folly. Pity the poor Savage owner that attempts to convince a state DNR that the more radical loads are anything but the equivalent of a single-shot .458 WinMag. Ballistically, they are not.

Anyway, that's my opinion-- the only one I happened to be equipped with. Neither Savage Arms, Hodgdon / IMR, Alliant, Olin / Winchester, or Accurate Powders disagrees. Nor does the man that designed the 10-ML in the first place.

Bullets and sabots will incrementally improve, as they have all along-- and the standard load performance of the 10-ML along with it (as well as other muzzleloaders). To dilute the true beauty of the Savage 10ML: clean, strong, sealed, corrosion-free, safe, accurate, reliable, mild recoil, economical cost per shot with promotion of experimental, non-approved bathtub gin powder columns is a tragedy. The competitors who have already clearly sought to derail the 10ML project since its inception could not have written a better prescription for its untimely demise, were they clever enough to do so.

To not raise questions and concerns about amateurish load development is to give tacit approval to it. No single human life or limb is worth taking unnecessary risks. Either you "know" or you "don't know" what they are. With today's impressive array of ever-improving propellants, sabots, and projectiles, assuming the risks associated with the unproven and unknowns is best left strictly to the ballistic laboratories and other experienced professionals that do this for a living.

That's my opinion, and I'm stuck with it-- and, sticking to it. I welcome yours.

[1SHOT-1KILL]

I can't argue with that, Randy.  Regardless of whether it's a 10ML, a 10ML-II, a TC Hawken, a Knight, a c/f pistol, a c/f rifle, or a c/f shotgun, that I am loading for, I keep it as simple as possible.  From day that the first 10ML was shipped from Savage, I had the feeling that one the things that the 10ML would have to overcome, so to speak, was that people would make it much more complicated than it really is or has to be.   The duplexing, not to mention triplexing,  is not only uncalled for, but throughout the shooting industry is totally discouraged.  

With the selection of powders available, like XMP-5744, IMR-4759, N-110, and Lil Gun, velocities with a 250gr bullet of 2,300+ FPS are the norm rather than the exception.  With Lil Gun velocities approaching 2,700 FPS can be had easily if one is not too recoil sensitive.  With that kind of performance, why take the unneccessary risk of experimenting with duplex loads?

[Stoneybroke]

As a new Savage owner, and a long time handloader, I've been reading posts concerning duplex and triplex loads with some concern.  If I understand the savage ML concept correctly, the sabot is essentially a pressure relief valve.  What I'm reading is shooters stuffing 28 ga cups, wonder wads, mmp sub bases, and God knows what else, down their barrels.  All this is done to defeat the pressure relief concept.  Has anyone pressure tested these "super" loads?  What are the credentials of the experimenters?  I really think somebody is going to get hurt!  Stoney

[RandyWakeman]

If I understand the savage ML concept correctly, the sabot is essentially a pressure relief valve.  

Nothing compensates for the loose nut behind the trigger. Speaking only for myself, the sabot is only an auxiliary pressure relief. Assume enough gas pressure is created to vaporize the sabot evenly (which has never been shown to happen). At best, the only allowable vent would be the flow allowed in the newly formed approx. 25 thousandths "ring" surrounding the .45 caliber (for example) projectile in a millisecond or so.

As is, the Savage is provably the strongest, safest, cleanest muzzleloader made. Only by ignoring the largesse of well-tested, well-proven loadings established over the years can one possibly compromise that fact.

[Stoneybroke]

Bottom line!  What are the pressures generated by these duplex and triples loads?.  Are these pressures repeatable with different lots of powder?  Are these pressures repeatable from shot to shot?  How do these pressures compare with the standard loads?  Aside from the fact that the experimenters have very large cajones, what other credentials do these folks possess?

[tmarch]

As far as credentials, I don't know of anyone with more credentials than Toby Bridges with the Savage and he's been doing some duplexing.  
Now don't get me wrong, I have no interest in duplexing or mixing powder in any configuration, but it is interesting to see what these guys are doing.
I'm more interested in working with lighter bullets and improvements with the sabots by themselves to get any improvements in ballistics.  Not that there's much need for improvements.

[RandyWakeman]

When I mentioned "and other experienced professionals that do this for a living," Toby Bridges certainly fills that bill. Toby's vast experience speaks for itself.

I'm speaking to the issue in the context of those who have less experience than Toby (most everyone on the planet), and the fact that no powder company or firearms manufacturer supports this. Unless one fancies them as expert as Toby Bridges in smokeless muzzleloading, they are far better off staying well away. Far, far away.

The last thing a new Savage owner needs is another powder to buy, or another complication to consider-- and it is not even remotely necessary or indicated. I personally feel it is a very bad scenario to promulgate to any prospective 10ML-II owner, or any game department. I can also tell you the exact number of duplex and triplex loads that the designer of the gun, Henry Ball, has fired over his smokeless muzzleloading lifetime.

That quantity remains at exactly zero.

[Stoneybroke]

Randy:  Essentially, we are in agreement.  We are preaching to the choir.  Stoney

[simonkenton]

You make a good case, Randy. Thanks for the informative post.
I have watched with some interest the boys discussing duplex/triplex loads over on the Savage forum, but I am not  interested, too complicated for me.

[RandyWakeman]

Naturally, part of the fun and challenge of muzzleloading is working up "your" load, the one that suits you and your gun the best.

However, when it comes to duplex / triplex / octoplex loads (perhaps for underwater use?), it is absolutely not allowed by the inventor of the Savage 10ML, Savage Arms, MMP sabots, Hodgdon / IMR, Alliant, Accurate Powders, SAAMI, etc., etc. That should send a very clear, cautionary note to most reasonable people. :roll:

Those who feel they are more qualified to instruct themselves in the use of the 10ML than Henry Ball or Savage Arms, or think they are more educated in sabot technology than Del Ramsey can do what they will, and do. They do so, however, against the strict warnings of all the above. It is a great pity.

[RandyWakeman]

You make a good case, Randy. Thanks for the informative post.
I have watched with some interest the boys discussing duplex/triplex loads over on the Savage forum, but I am not  interested, too complicated for me.

I’ll take the title of "Mr. Anti-Duplex" anytime one wishes to bestow it on me—for good reason.

The amateur duplexers are ignoring basic physics, and apparently have little appreciation for the tremendous amount of powder development man-hours and the redundant radial transducer testing used to develop today’s powders. One may ask “why?” Though duplex loads do not work, says Richard Lee and others, and are very dangerous—and are warned against by every senior ballistician I’ve ever worked with in the years past, that still isn’t good enough for some people.

I.   POWDER IN BARREL:
There is nothing to show that pouring down an initial charge in a muzzleloader will not leave some, inconsistent amount of powder sticking to the barrel sides, or inside the rifling. How much, with what powder, is speculative—contingent on barrel and barrel condition (fouling).

II.   USE IS UNPREDICTABLE IN THE SAVAGE 10ML-II:
The 10ML-II breechplug is full of air, in pre-firing state. Once a primer is ignited, that air is forced into the powder charge in a fraction of a millisecond, before the flame can even get to the powder. That air velocity changes with breechplug fouling, vent-liner erosion, etc., and the speed-up due the “Venturi effect” (or stepdown from breechplug hole) will vary from shot to shot, gun to gun.

III. POWER CHARGE IS UNCOMPRESSED AND MIXED DUE TO AIR TURBULENCE:
The .030” vent liner is in the center of the .50 caliber barrel. The rapid air pressure destroys the previous powder compression, disturbing the “layer cake” duplex condition that can exist only under perfect conditions. How EXACTLY this jet stream disperses the “lower powder” into the “upper powder” is contingent on that powders’ grain style, weight, and volumetric measure density—as well as that barrel’s bore tolerance, rifling tolerance, sabot / bullet combination used, and powder column height. This initial airburst cannot push all the lower powder forward as a unit; a small hole in a .50 caliber bore makes that impossible.

IV. PRIMER PRESSURE
Every breech plug will exhibit initial air flow differently, contingent on breechplug carbon, primer brand, primer tolerance, specific vent-liner, and so on. Resultant powder turbulence will vary in concert with this.

Change a primer brand, you change pressure. Change a sabot or bullet, you change pressure. Change one single powder, much less two-- you change pressure. Change the condition of breechplug or ventliner, you change pressure. Change barrels, you change pressure. ANY shotshell reloader knows you can change pressures by 15% or so just by a 209 primer brand change, or a wad change—from a “Windjammer” to a “Federal” wad. In the Savage 10ML-II, we are using the same primers. A sabot is the gas check, just as a shotshell wad is. To make matters worse, a breechplug full of air does not exist in shotshell reloading. Loads should not be “proven unsafe,” they should be PROVEN AS SAFE.
DUPLEX LOADS ARE ERRATIC AND DANGEROUS. They are unpredictable for all the reasons cited above.

I am well aware of Savage 10ML-II barrels that HAVE been irreparably damaged SOLEY with repeated use of duplex loads. The Savage 10ML-II is the best-built, strongest muzzleloader on the market—but even the best can be abused, misused, and damaged. Duplex loads have already done just that. If you duplex, you do so at your own risk. The sad thing is—they are not even remotely necessary for any hunting or shooting application. It is needless, unnecessary risk.
NO FACTORY APPROVED LOADS HAVE EVER DAMAGED A 10ML-II.

If this little missive saves but one injury to shooter or innocent bystander, it is well worth the irritation of whatever mudslinging or name-calling it might evoke.

The Savage is the strongest muzzleloader made, some say the strongest rifle made. But, any product can of course be abused. By staying within Savage's rules, Savage 10ML fans can work together to keep this firearm what it was designed to be from its inception-- Safe, Clean, and Simple-- and the very safest muzzleloader ever introduced. That WAS the motivation for its development-- nearly 14 years ago.

[grouse]

I used to read a little bit about the Savage over on Toby's sight.
All those duplexing loads and not shooting when it's warm out, and
guns not going bang. Well, that was a big turn off to to me. Glad i have found out differently since then.

[simonkenton]

Grouse-- What way have you found to overcome the problem of loss of accuracy in warm weather?
I was shooting my Savage on  70 degree days and I had bad problems with barrel heating. I could not get the thing to group. I took a cooler with ice cubes out and would run an ice cube up and down the barrel between shots, that didn't work.
I just had to wait 15 minutes between shots to get it to group. This is the only thing I dislike about the Savage.

[grouse]

Grouse-- What way have you found to overcome the problem of loss of accuracy in warm weather?
I was shooting my Savage on  70 degree days and I had bad problems with barrel heating. I could not get the thing to group. I took a cooler with ice cubes out and would run an ice cube up and down the barrel between shots, that didn't work.
I just had to wait 15 minutes between shots to get it to group. This is the only thing I dislike about the Savage.

     I dont have my Savage yet. Maybe this week. It seems to me that
5744 powder and the Media blast on the Henry Ball Savage will keep
my accurracy consistent. Atleast i hope so.

[RandyWakeman]

What way have you found to overcome the problem of loss of accuracy in warm weather?
I was shooting my Savage on  70 degree days and I had bad problems with barrel heating.

Do you have a blued barrel, Simon?

41 grains of 5744 you can shoot all day with a 250 gr. sabot, as fast as you want-- and still hold 1 MOA or better on 77 degree days. That's been my experience with the std. Savage 10ML-II Stainless.

[simonkenton]

Yes I have the blued barrel.

[RandyWakeman]

Yes I have the blued barrel.

That's a big part of it, I'm afraid.

[simonkenton]

Well I have a shiny new can of 5744 here and I hope to get out this week. I am gonna try 40 gr of it and see if I can get off shot after shot without waiting. I am not patient and I dislike very much only getting 4 shots per hour.
At any rate, a hassle at the range is no detriment to the hunter, and hunting is why I got the Savage.