pressures of various loads/BP vs. smokeless

[rifle]

I am under the impression that smokeless is perfectly fine when used in cartridges fired from the "conversion cylinders" sold by manufacturers like Kirst and R&D Gunshop. Doesn't it say on the web sites that the conversion cylinders are recommended to be used with blackpowder loads or commercial factory made "Cowboy" ammo?  Cowboy ammo is smokeless and approximates the lower pressures of black.
Comparing blackpowder pressure curves to smokeless pressure curves the big difference,if not in peak pressure, is the "time" it takes the powder to reach peak pressure. Smokeless puts more pressure to the curve faster than blackpowder. That makes more stress on the guns. I think of it kinda like blackpowder is like a wide swing of a punch and smokeless is like a straight forward karate punch.
Anywhoooo, I had Kirst conversion cylinders for Remies and own R&D conversion cylinders for them now(not that R&D is better than Kirst) and have no problem with using smokeless "Cowboy" loads in them. The manufactures recommend the use of smokeless Cowboy ammo as well as blackpowder ammo. There are Cowboy loads listed in reloading manuals too. Some of the Cowboy loads are within the realm of regular standard loads. Some Cowboy loads are more pressure and energy than some standard non-cowboy loads. I use smokeless Cowboy loads in my conversion cylinders since the manufactures recommend it.(unless something has changed that I don't know about) There are Cowboy loads in manuals and ammo sold in the stores by factory manufacturers that use 250gr. bullets at a respectable velosity. It would take a real tough hog to be unaffected by one of those 250gr. bullets traveling at a good velosity.Goex FFFg powder at 35grains volumn can push a 250 grain bullet to just a tad under 900fps. That is a recommended load of blackpowder that won't hurt the gun and would definitely put the hurt on a wild boar.
What's the talk of guns turning into grennads when used with smokeless loads? Has the manufacturers recommendations changed concerning the use of factory smokeless "Cowboy" loads?

[w44wcf]

Rifle,

Smokeless puts more pressure to the curve faster than blackpowder.

I'm thinking that it is the other way around .........because black powder will bump up an undersized lead bullet quite well, smokeless much less so.

Where folks get in trouble with smokeless, especially the faster burning powders, is that it only takes a grain or 2 extra to really increase pressures, or much worse, a double charge whch can take pressures to over 50,000 psi!!!

The earliest smokeless powders (DuPont No 1 Bulk Smokeless & DuPont No 2 Bulk Smokeless) were bulk for bulk,  meaning that the same volume of smokeless and the same volume of black powder generated the same velocity and pressures.

Then came "Dense" type smokeless powders, which are what we have today that uninformed folks can get into touble with. 

w44wcf

   

[Fox Creek Kid]

I'm thinking that it is the other way around .........because black powder will bump up an undersized lead bullet quite well, smokeless much less so.

Nope, smokeless has an initial pressure spike.

[Adirondack Jack]

Nope, smokeless has an initial pressure spike.

The bit about obduration is misleading.  BP bullets tend to be softer and more amenable to obduration, whereas common smokeless bullets have to be smacked pretty hard to obdurate as they are usually too hard.

[w44wcf]

Fox Creek Kid & Adirondak Jack,
Please consider the following and let me know what you think.

A few years ago I worked with b.p. and smokeless under 50/1 lead / tin bullets in my '73 Winchester .44 W.C.F. 

The rifle has a .433" groove diameter. 

Bullets were from a Lyman 427098 mold and were .428" in diameter.

Thus, the bullets were .005" smaller than the groove diameter.

With b.p. the rifle would group into 2" @ 50 yards with all bullet holes nice and round .  Not bad at all.

With smokeless, accuracy was hopeless (12+") with all  bullets keyholing.

I would say that would indicate that the b.p. has an immediate sharper pressure curve which obturated the bullet to fill the groove and thus produced accurate shooting.

Whereas, the same soft alloy bullets propelled by smokeless did not obturate to fill the groove and went merrily on their way.

Also, another much more schooled in this matter had posted this some time ago:
"The reason for wads is that BP has a sharp peaked pressure cure and the wads protect the gases from disforming the base of the bullet. Smokeless powder has an arched pressure cure and does not disform the base of the bullet with moderate pressure."  

Sincerely,
w44wcf

[Fox Creek Kid]

F.W Mann proved over 100 years ago that with BP the base of the bullet obturates completely BEFORE the bullet even leaves the cartridge case. That is why your BP loads shot so well (along with other factors). Smokeless has an initial pressure spike GREATER than BP but also very short, hence that is why smokeless rounds are far more prone to lead (actually it's "tinning") the forcing cones and barrel. BP is an explosive and smokeless powder is a propellant.

[Adirondack Jack]

On obduration:

BP MAY provide and advantage because it provides both a prolonged pressure wave and sufficient wallop to obdurate the bullets instantly.  Part of the reason a BP charge does in fact obdurate the bullet instantly (before the bullet moves) is that there is no air space in a BP or sub load.  The air space in a smokeless load acts like a air damped screen door closer, so the bullet does NOT move right away in most cases, as all that air has to be compressed before the bullet gets shoved out of the way, and that air acts to cushion the shock of the firing upon the bullet base.

In my work with my Cowboy .45 Special cases, which of course offer very limited case capacity, I found that I could get instantaneous obduration and case seal (when ya see powder stains down to the exact level where the bullet base was, but not below that level, with a clear line of stain, ya know yer getting instant obduration, as the pressure necessary to instantly seal cases is also enough to obdurate lead) I also see NO leading with straight WW bullets with either smokeless or 777, indicating the bullet gets obdurated not once but twice. (first in the chamber, then in the forcing cone, after being extruded through the throat).

With .45 Colt, I had to run VERY warm loads to see decent case seal, and never did get great obduration out of WW lead with smokeless  unless running em too hot for CAS (900+ fps).  The difference clearly is the amount of air in the case and the fact that the air gets to act as a pneumatic cushion.

Jake McCandles notes his C45S Goex loads result in cleaner cases than the average .45 Colt case comes back when shooting smokeless.  Same deal.

[rifle]

I've seen pressure curves of black and smokeless plotted on the same graphs with the intention of observing the differences. The black goes up slower and doesn't reach the same pressures as smokeless that goes up faster than black and goes higher and comes down faster.  The black takes longer to reach peak pressure. Pushes longer.  Black is an explosive and smokeless is a flamable. Why that is I don't recall. They both burn and they both create gases but what designates one a flamable and one an explosive I don't recall at the monent.

[Adirondack Jack]

I've seen pressure curves of black and smokeless plotted on the same graphs with the intention of observing the differences. The black goes up slower and doesn't reach the same pressures as smokeless that goes up faster than black and goes higher and comes down faster.  The black takes longer to reach peak pressure. Pushes longer.  Black is an explosive and smokeless is a flamable. Why that is I don't recall. They both burn and they both create gases but what designates one a flamable and one an explosive I don't recall at the monent.

BP  is classed as an explosive because it burns at the same rate regardless of confinement.  Pour it on the ground and touch it off, ya get the same burn rate as in a gun.

Smokeless requires confinement to burn very fast, and the progressive nature of smokeless means the more pressure it is under, the faster it burns.  Therefore smokeless in a weak container is relatively fire safe (it just burns) whereas BP will explode.  That's why DOT considers smokeless a propellant and not an explosive.

The graphs you observed were likely at "service" load levels, where there is enough smokeless present and sufficient charge density to get a good burn.  At CAS levels, there is often LESS pressure when using smokeless, especially small amounts in big cases.  You do get a steeper spike, but it may not be all that high a spike and it may not last very long at all.  Think in terms of a tack hammer swung hard VS a dropped sledgehammer

[TAkaho kid]

Hello 44WCF, Etal,

One big issue with BP and slugging-up bullets is the solid partical matter. Remember that nearly 50% of the charge becomes residue. This column of solid matter and not yet burned powder (burning from the primer forward) slamming into the base of the bullet makes a heck of a diffrence. Sort of like sound traveling through water versus air.

Best regards,

T.K.

[w44wcf]

Guys,
Interesting discussion. I think all of what you fellas have indicated have merit. 

Traces of smokeless pressure illustrations that I have seen have all been over 40,000 p.s.i. which is way over the 12,000-20,000 p.s.i. b.p. realm.  Perhaps, traces of smokeless at b.p. pressures would not spike as quickly(??).   

Perhaps the faster burning smokeless (Bullseye, 231, Unique, etc.) might  give a quicker spike.....but I think that the slower burning smokeless powders such as 2400, 4227, 4759, 5744  in  b.p. cartridges do not.   

I do know that a capacity load of RL-7 will duplicate b.p. velocity and pressure in the .44-40.  I have found that it will not bump up the bullet like b.p.  I also found that PYRODEX doesn't either.

I will be heading to the Cast Bullet Rifle Silhouette Championship in Ridgway, PA and will be out of touch for the next several days.  When I get back, I will dig deeper in my reference material to see if I can find anything pertinent.

Sincerely,
w44wcf

[Driftwood Johnson]

Howdy

Here is a pair of pressure curves that Old Scout emailed me a couple of weeks ago. I have been looking for a comparison of BP vs Smokeless for a long time, this is the first one I have gotten my hands on.



Old Scout tells me he plotted these curves around 1958 using a "Dual trace storage scope ( Fairchild I think ), piezoelectric transducer pressure gun, and a Polaroid camera." Whatever all that is. Obviously he drew the curves by hand, but there is the equipment he used to get the data. Pressure is in PSI, the time scale is plotted in milliseconds.

This pair of curves is for shotgun loads. He does not recall exactly what the Smokelss powder was, he thinks the BP was Gerhart-Owen FFg. I believe that is an early name for Goex. The two loads tested were 3 dram, 1 1/8 ounce 12 gauge loads. 82 grains of BP is 3 drams. The 18 grain unknown Smokeless load achieved the same 1200 fps velocity as the BP load.

Knowing the specific Smokeless powder in this case is not important. The shape of the 2 curves is very instructive. I find it interesting to note that for the first half millisecond the BP pressure rose more rapidly than the Smokeless pressure. But the BP pressure began to level off rapidly and was soon completely overtaken by the Smokeless pressure by about 1/2 millisecond. The Smokeless pressure continued to rise very rapidly and peaked before 1 millisecond had passed. Then the Smokeless pressure dropped very rapidly, dropping lower than the BP pressure just after the first milli second. The sharpness of the Smokeless pressure spike is very evident here. Not only was the pressure higher than the BP ever achieved, th spike is much shorter in duration.

The other very interesting thing to note about the two curves is they each have a small spike immidiately after time zero. That is the pressure spike generated by the primers. The BP curve acutually dropped directily after the primer fired, while the Smokeless curve continued to build after the primer fired.

Hope this is of some use.

[Fox Creek Kid]

Thansk for the chart Driftwood. I've spoken to Richard (Old Scout) before and he's a veritable encyclopedia on firearms/gunsmithing.

[Adirondack Jack]

I note the chart above is for shotgun, where there is 100% charge density and wad compression to boot with the smokeless load.  (FWIW:  I'd hazard to guess the 18 grain load is something on the order of 700X or some very similar burn rate powder.  The results are consistent with something close to that)


I'd love to see the charts on a CAS level load of Unique or some similar powder VS BP shot at the same velocity out of .45 Colt or .44 manglem cases.
Wonder what the effect of the big ole case with a scant fingernail full of powder rattling around in it is VS a full case of BP.

I know my pard Jake McCandles is getting case seal with Goex and a 200 grain bullet in the C45S case (about 18 grains of Goex), and I can get cases to seal with a 700X load at the same velocity.  In .45 Colt, ya can get fair case seal with BP, but can't get it with smokeless at the same velocity.

I'm still thinking it's about the pneumatic "shock absorber" effect of the air in the cases.

[Driftwood Johnson]

Howdy Again

I'd love to post more charts. Unfortunately I don't have any. Old Scout sent me this one a couple of weeks ago. When I asked him if he had any more he said he had gotten rid of most of that stuff a long time ago.

[Steel Horse Bailey]

Howdy Again

I'd love to post more charts. Unfortunately I don't have any. Old Scout sent me this one a couple of weeks ago. When I asked him if he had any more he said he had gotten rid of most of that stuff a long time ago.

Howdy!

Too bad - this has been very interesting and runs with all I've ever heard about powder properties.  To borrow from my pard Dick D, "There's learnin' goin' on here!"

Thanks, Driftwood, AJ, 44 WCF,  FCK and all y'all others.

[w44wcf]

Driftwood, thank you for the chart.  Very Informative!   It definitely shows that the black powder produces a much quicker initial pressure spike in your example.

I just had an interesting discussion with Jim Ristow of "Shooting Software".  From what has seen, he indicated that b.p. does have a sharper initial pressure spike.

http://shootingsoftware.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=RSI&Category_Code=PT

When I get a few extra $$ together,  I think I will pick up the PRESSURE TRACE INTERNAL BALLISTICS SYSTEM.  Should be interesting.

w44wcf

[Driftwood Johnson]

Howdy w44wcf

Judging just from this one chart, I would not interpret the initial pressure spike of BP to be sharper at all. Maybe it's just symantics and what we mean by 'sharper'. Ignoring the initial spike of the primer, the curve for BP begins to flatten out as time progresses much more quickly than the Smokeless spike. Although the pressure is still increasing with the BP curve, the rate it increases begins to decline almost immideately. That's what the convex shape of the curve indicates. The Smokeless curve on the other hand is concave for almost the first half of its rise, indicating that the rate the pressure is increasing is also increasing as the pressure itself increases. The Smokeless curve also drops off much more sharply than the BP curve.

Now I am no expert, but I have always heard that it is not just the higher pressure with Smokeless, it is also the duration of the spike that can do the damage in a gun of questionable strength. The idea is the sharp increase and decrease hits the steel like a sharp hammer blow, and the steel cannot accomadate the rapid pressure spike as well as it can with the slower rate of pressure increase with a BP curve.

This chart was generated by the pressures of two loads of Smokeless and BP that produced the same velocity with the same projectile. It would be very interesting to see the curves produced by two loads that peaked at the same pressure, regardless of the weight or velocity of the projectile. I would be really interested in seeing that comparison. I would suspect that if both curves showed the same amplitude, the Smokeless spike would still be much narrower than the BP spike. Unfortunately, this is he only chart that Old Scout had to send me.

I would love to see some charts that you produce when you get your equipment. It should be very instructive.

[Adirondack Jack]

Driftwood, I tend to agree.  Some of the old case hardened stuff simply was not ductile enough (if that's the right word) to stretch and return to shape when smacked with a sharp blow from smokeless.

I'd liken BP to hitting something with a green stick, and smokeless like hitting it with an axe of the same weight.  Same momentum, way different initial shock.  I don't suppose ya could break cast iron (as an extreme example)  with a wooden stick, but ya sure can with an axe.

[Driftwood Johnson]

AJ

I don't really think case hardening has anything to do with it. At least with revolvers, it was only the frame and parts like the hammer and trigger that were case hardened. These parts did not see the pressure of the cartridge firing. The cylinder and barrel were never case hardened. It is the cylinder that sees most of the pressure of the cartridge firing. If anything is going to give, the cylinder is the most likely candidate.

Ductility is the mechanical property of being capable of sustaining large plastic deformations due to tensile stress without fracture (in metals, such as being drawn into a wire). It is characterized by the material flowing under shear stress. It is contrasted with brittleness. (Wikipedia). Think of very hard rubber, which may be relatively strong, but will yield before it breaks. If the forces applied are not to great it will yield, then return to it's original shape. What we are talking about is tensile strength. Tensile strength measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. (Wikipedia again)

Case hardened frames are only hardened on the outer few thousandths. This was done to harden the outer surface for wear resistance. The inner bulk of the metal retained its original ductility and could take the mechanical shock of recoil very well. Cylinders on the other hand have the same tensile strength through out the part. Very early Colt SAAs had maleable iron frames and cylinders. Malleable iron is not really a true steel. Later versions used a relatively low carbon steel by modern standards. Even so, Colt did not guarantee the SAA to be safe with Smokeless Powder until 1900, when metalurgy had advanced enough to reliably produce stronger steel at reasonable prices. Sometime around the mid point of the 20th Century most gun makers started hardening their cylinders, which further added to their tensile strength. This type of hardening changes the hardness of the steel completely through the entire piece. When it is done correctly, the tensile strength of the part is increased. When it is done badly the part becomes brittle and breaks easily. But it is very hard. Think of ice as an example of hard and brittle, but very weak. It was this type of hardened steel that allowed high pressure cartridges like the 357 Mag to be chambered in cylinders with relatively thin cylinder walls, like the S&W Model 19. Prior to that time, S&W only chambered the 357 Mag in the much bulkier cylinders of N frame revolvers. The thicker chamber walls made up for less tensile strength in the material. When stronger steels became practical through advanced hardening techniques, the 357 could be safely chambered in the smaller cylinders, with their thinner chamber walls, of K frame Smiths.