Velocity limit of black powder
Retrieved: 10/20/2016
Last Post: 10/12/2016
Gunpowders have a maximum velocity obtainable because they have to push the weight of their own combustion products down the barrel along with the projectile, so even with the lightest bullet possible, the velocity will be limited. With smokeless powders this limit seems to be under 5,000 FPS. Parker Ackley invested a lot of time and money trying to get to 5,000 FPS and probably didn't make it. I say probably because he used a ballistic pendulum to measure muzzle velocity, an imperfect instrument at best.
After a debate about Civil War sniping, I looked up the velocities quoted for replica muzzle loading rifles. A little over 2,100 FPS seemed to be top. I would guess that the velocity limit would be lower than smokless simply because the lower pressure gas has to push all the solid particles in the smoke ahead of it. Threads about black powder cartridges are vague about velocity. BTW, I am referring to real block powder, not one of the substitutes.
wesg
10-03-2016
There's also the idea the gas can't expand any faster than the speed of sound in it. So the hotter the better, which is where smokeless has an advantage.
CalG
10-03-2016
The "speed of sound limit" theory has been "dis-proven" by the efforts of interested air gunner's. I believe the record at present is over 1800 fps. But of course, the question remains about the temperature of the propelling air. After all, the velocity of the molecules is averaged. some are at zero, and some are going very fast. Which are driving the projectile?
For shitz and giggles, look into "light air guns" The velocities obtained are truly amazing. 'set your nose crooked' . ;-)
Monarchist
10-04-2016
Quote Originally Posted by 9100
After a debate about Civil War sniping, I looked up the velocities quoted
for replica muzzle loading rifles. A little over 2,100 FPS seemed to be top.
(Successful) 'sniping', even if we presume long(er) distances, mostly, did not/does not require uber-velocity, nor uber-flat trajectory.
What it requires most of all is repeatable predictability. Sufficient retained energy as well. 1860's heavy, but VERY well stabilized projectile was the precision rifleman's tool. The counter to it was more likely to be cannon and canister shot as counter snipers.
With repeatability, one can make use of skill/instruments/both to gauge and adjust for flight time, winds, ground level and aloft [1], Earth's rotation, etc.
ABSENT predictability, velocity alone cannot help.
Those among our predecessors as sought 'the limits' were also among the first to back down FROM them a notch or three and work in a more practical and repeatable comfort zone.
[1] More than one of the "Project HARP" tubes achieved muzzle velocities in excess of 7,000 FPS. Artillery, 'Naval Rifle', and tank main-gun, not shoulder-fired, 'sniping' , AKA "first round hit or take the consequences" is a first-order coondingie tightener, but in the interests of accuracy, (and tube life..) generally worked at somewhat lower velocities.
9100
10-04-2016
There are a number of ways to produce hypervelocities and Gerald Bull probably tried most of them. The question wasn't about them or even black powder snipers, but about the propagation velocity of standard black powder.
Actually, Mach 1 airflow isn't hard to achieve. Things like vortex tubes reach it internally at a relatively low air pressure. I have made torches that have shock lines in front of their nozzles. The issue is whether black powder can push all those particles faster.
CalG
10-04-2016
A little off the mark, but this is worth looking at Smooth Bore Cannon Ballistics
3 mile limit...;-)
jabezkin
10-06-2016
Check out the
velocities of the Paris Gun.
9100
10-07-2016
They got to 5,400 FPS, but the Paris guns had booster charges that lit off as the projectile passed them. It is doubtful that they could have reached that velocity with a single charge in the breech. You probably could exceed that velocity by attaching a charge to the projectile, making a gun/rocket hybrid. A typical space rocket uses most of its fuel adding kinetic energy to the remaining fuel so it continues to accelerate, reaching speeds higher than the basic exhaust velocity of the rocket engine. The best ones also use LH/LOX, wh ich has a combustion product molecular weight of 18 (H2O, water), which produces a much higher exhaust velocity that normal gun powders.
Of course, none of this uses black powder.
This does bring up an ancillary question. Our little space effort, Gateway Space Transport, now defunct, used a jet engine fueled by normal kerosene and kerosene/LOX rockets. It occurs to me that we could have used hydrogen for the jet fuel and LH/LOX rockets for a considerable gain. The normal immediate reaction would be that hydrogen would burn up the jet engine, but not so, you would only feed enough hydrogen to reach the rated exhaust temperature.
There is a story around that Gary Powers' U2 ran out of LH used to boost his engines, making him fly lower, within SAM range.
BTW, does anyone need a Turbomeca Marbore IIA jet engine? I have a nice one for sale.
Thumann
10-07-2016
The Paris gun did not have booster charges.
Forestgnome
10-07-2016
Wouldn't this be the same as calculating hydraulics? So for instance you would use the chamber surface area as one piston area, and the area of the base of the bullet as the other piston? Then calculate for force? Then the bullet velocity would be calculated for acceleration based on mass and force applied. So the limit wouldn't be the expansion rate of the gas, rather the volume of the chamber vs. the bore diameter.
CalG
10-07-2016
Simple math? Yes. Up until the point that the surface that is under pressure is receding at a rate faster than the arriving (expanding) gas molecules.
Pressure (acceleration/ velocity) can come from many combinations of momentum transfer.
Forestgnome
10-07-2016
I didn't mean to say calculating the acceleration would be simple, however the greater the ratio of chamber volume to barrel volume, the less effect on pressure there would be due to the bullet travelling down the barrel. At some point the theoretical pressure peak would be post bullet exit as the chamber volume is increased.
CalG
10-07-2016
On this side topic... I've asked the question on other forums. Has anyone come across a comparative chart of various smokeless powders and their gas generation "factors"? Vihta Vuori publishes such data for their own powders, but make no comparisons to others. Burn rate comparison charts are quite common. Even if they may be the same data rehashed and reprinted. I've seen some confusing listings for H335...;-)
9100
10-07-2016
Quote Originally Posted by E.F. Thumann
The Paris gun did not have booster charges.
I could have sworn that I read a description of booster charges on the Paris guns, but it appears not. They were used on the V3 in WWII. The search also turned up this paper describing projectiles with propellants in their bases, the gun/rocket hybrid I mentioned earlier. http://www.dtic.mil/dtic/tr/fulltext/u2/a203307.pdf local copy
The paper comments on the problem with simply increasing the charge- the extra energy needed to force the combustion products down the barrel, which was the starting point of the thread. Eventually you will reach a point where additional gunpowder doesn't increase projectile velocity.
Re the larger volume of LH, you do have to drag along a much larger tank. A carbon atom attaching to two oxygen atoms yields about the same amount of energy as four hydrogens reacting with two oxygens, but the combustion product of carbon, CO2, has a molecular weight of 44 while the hydrogen product is H2O, water, with a weight of 18. That makes a huge difference in the thrust produced and hydrogen powering a jet engine would get a lot more thrust per pound of takeoff weight since it doesn't have to schlep along its oxygen supply. Burning hydrogen gives the same amount of energy as three times the weight of carbon. When you get into VTOL vehicles, the difference in performance would be spectacular.
partsproduction
10-10-2016
I've often wondered about this as well. The German WW2 V weapon used a multitude of side chambers, and I wonder what kind of limit one might reach with that using BP.
I also wonder if Gerald Bull experimented with that concept using smokeless.
I also wondered about gun shells, shells with loaded charges and projectiles that would fire just outside the muzzle of the larger gun, and I suppose even a third gun would be possible, the inverse of tree stage rocket engines, the first large gun shoots the smaller gun, which doubles it's velocity because it's moving already, and the third shell gun benefits from the velocities imparted by the other two. These things actually make sense in rarefied atmospheres and space.
Above a certain velocity a round pellet explodes into a gas plasma with fantastic results. I've seen photos of dust particle impacts on the surface of aluminum (I think) at tens of thousands of miles per hour, they can hurtle along for millennia holding their velocity, crossing vast distances in space. The same particle accelerated to such velocities in our atmosphere would become harmless quickly.
I understand the new rail guns achieve very high velocities with finned projectiles, and the smoothbore Rheinmetall 120 MM tank gun reaches 5700 FPS maximum. (I wonder how they do that)
For sniping I always thought a long boatail should be pretty predictable at BP velocities, but there is more time for variables to effect them, including time for the target to move.
BTW, about the Paris gun, long ago I read that the turntable needed 8" hardened steel balls to roll on, and they bought them secretly in the USA. The Paris gun put first man made objects in the stratosphere.
9100
10-11-2016
Quote Originally Posted by jabezkin
You need to do some research........before you post. Lol
In what respect? I am certain I saw a statement that the Paris gun had boosters many years ago, long before the internet. I have followed firearms for 68 years and have only found the one paper I referenced about traveling charges, although I knew it was possible. The rest of my statements are correct.
partsproduction
10-11-2016
do some research
Or better yet, don't read such thought provoking threads.
After searching for an hour for data on the Paris gun turntable's 8" diameter American made ball bearings (96 for each turntable) I found very little, so I spent next weeks grocery money on a book about it. It could have been worse, had I purchased the Paris gun book written by two scientists, including GV Bull (Yep, one and the same), it would have cost a couple weeks worth of vittles. My wife doesn't understand the buying of books.
Very interesting thread I say because I've often wondered why large bores were used for sniping during the civil war (The war of Southern aggression. ) I hadn't ever considered that there was a limit to the velocity potential of black powder.
The answering post mentioning the higher heat of smokeless gasses rings true, because with out the heat of millions of degrees a thermonuclear explosion couldn't happen, it's the super rapid expansion of those millions of degrees heat to the air around the blast that causes blast damage I believe.
A hint lies in Diesels computations for thermal efficiency of his engine, the heat being held at the flame temperature during expansion by controlled addition of fuel during the power stroke.
So, as to black powder velocities, I wonder if anyone ever tried carrying the charge with the projectile so that freshly burning gasses are added to the column at the projectile end instead of the breech end where it has to push that long column of gas? Said moving cartridge might separate at the muzzle. The aim here is maximum velocity, not accuracy. (Gyrojet, but it did not use pressure but thrust instead.)
GGaskill
10-11-2016
...I wonder if anyone ever tried carrying the charge with the projectile...
Once again you run into the problem of accelerating the powder gas although in this case, the powder is still solid. I am not in a position to do the math on this (have forgotten most of the calculus I learned 50 years ago) and that is what would be needed, along with some burn rate data and other things.
capital7
10-12-2016
Hmmmm, could work sort of like a tracer round, where the propellant is located inside of the round...
Interesting idea, if I didn't live in Canada I would try it :p
calvin b
10-12-2016
With all due deference. I believe the gun that you seem to have confused with
the ww1 (Big Bertha) Paris gun is the ww2 Hochdruckpumpe or HDP (nicknamed
variously 'Fleissiges Leischen' or 'Tausendfussler') Suffice it to say I'll
leave a accurate translation of those nicknames to some one whose first
language is German.
Just as a side note rocket assisted projectiles have been around with some
success for quite some time now.
As to your original question I don't know what the upper velocity limit of BP
is. I do know that the civil war era snippers tended to compensate for the
limits of BP velocity by using mass... ie heavy projectiles... I have
personally handled (and shot) a Civil War sniper rifle that was "liberated"
from a Union baggage train near Culpepper va that had a mold that produced a
700gn projectile.
partsproduction
See the link I posted earlier
http://www.dtic.mil/dtic/tr/fulltext/u2/a203307.pdf
The original Volcanic rifles and pistols used a hollow bullet with the charge
inside but the volume was too small. For such a rifle to develop serious
velocities, the projectile would probably need to be a sabot with a bore large
enough to hold a reasonable amount of propellant in a short package and a
smaller bullet to keep air drag down.
Re HARP and orbital launches, they still would need to launch a rocket because
it would need an orbital insertion burn at the top of the trajectory.
BTW, it takes more energy to reach earth orbit than the moon. For a moon shot
you just aim where the moon is going to be and fire away. An orbit requires a
delta V at apogee. A few years ago someone was wondering how to launch a bag
of gravel in reverse to the geosynchronous one of communications satellites.
Launching with the earth's rotation, you get close to 1,000 MPH head start. At
the time, no one had a rocket capable of making up the 2,000 MPH difference
going the other way. He found that he could do a moon shot instead, looping
around the moon and returning to the other side of earth orbit, do an
insertion burn, then release the gravel and destroy virtually all satellite
communications in a half day.
Come to think of it, Putin might do that if things get really tense because it
would shut down so much of our communications and wouldn't bother the Russian
Molniyas
So basically an easy test. Get a .50 caliber BP barrel and make a long brass
projectile with 300 grains of triple F, and with a perforated end plate
screwed in at the butt end. The holes not to provide thrust but just to keep
the charge moving with the projectile, then chronograph the result. It could
be a smooth bore for the purposes of the test, but should obturate around the
projectile so gasses aren't leaked.
Big Bertha is not the Paris Gun.
I stand corrected... after some research I see that 'big bertha' was the
allies nickname for 'dora' the German 800mm monster used in the siege of
Sebastopol. Not trying to flog a dead horse but I do seem to remember the
Paris gun having a nickname and in my some what foggy memory 'big bertha'
rings a bell. If anyone else has heard this please pipe up.. Nick names and
slurs from one war tend to pop up in other conflicts.
The simple answer to the OP's question lies in the chemical properties of
black powder as opposed to smokeless powder. Smokeless is classed as a
propellant that burns over a short time period of time, producing a gradual
increase in gas volume and pressure. Black powder is considered an explosive,
which releases chemical energy in one violent reaction. This pulse of energy
occurs in such a short time, and produces such a high volume of gas, notably
at one point, that the physical tensile yield values of the projectile and the
barrel are reached before a great velocity is reached. Regards, Clark
This pulse of energy occurs in such a short time, and produces such a high
volume of gas, notably at one point, that the physical tensile yield values of
the projectile and the barrel are reached before a great velocity is
reached.
But progressive shapes to retard burn rate goes back a long way. The bigger
guns used "brown" powder which was heavier in fuel, it burned much slower
allowing peak pressures over a longer time.
Thinking along these lines I looked it up and found this from 1918;
Scientific American - Google Books
Pretty interesting stuff.
The apex of black powder tech was reached during the paper patch era. It is
interesting to note the length the cases maxed out at in relation to the
length and weight of the projectiles. For rifles of caliber .45, the cases
maxed out at about 3" with 2.4 and 2.6 being more common than the longest of
the cases, while the projectiles maxed out at around 550 grains. The paper
patch removed the lead fouling issues in regards to the lead to alloy compound
of the bullets coupled with the relatively high velocities the bullets were
being driven. It is well known in black powder circles that any more powder
(longer case with increased capacity) even under extreme compression
(compressed case charge) yields no improvement as the unburned excess of
powder simply blows out the end of the barrel unburned. What this tells us is
that black powder is essentially self limiting by its burn rate. For that
reason alone, increased burn characteristics, smokeless powder with its
inherently superior qualities would relegate black powder to the dustbin of
history. I think it is important to remember that at its outset, smokeless
powder offered little advantage in regards to corrosive qualities in
comparison to black powder largely due to the very corrosive primers which
were used at the time, however the advantages of smokeless were obvious.
Originally Posted by sealark37
Not really. Both black powder and smokeless powder are classified as "low
explosives". They do not produce a shock wave in open air like high explosives
do. They need to be contained to produce an explosive force.
Originally Posted by sealark37
Yes... Sorta... Except that you are ignoring the fact the black powder
deflagrates, just like smokeless powder. That means the the flame front moves
through the material at subsonic velocities. If it detonated, you would
destroy the barrel. A detonation has a flame front that moves at supersonic
velocity through the barrel.
Velocity of the projectile doesn't come from the velocity of the flame front
through the material. It comes from the velocity of the gas expansion.
The Germans tried making a very long cannon to reach to London. They built one
into a hill. This was the cannon that tried to add more powder charges as the
projectile went up the barrel. They were never able to get the timing
right, and the experiment was a failure. I can't recall if the cannon is still
in existence.
The Paris gun had to use numbered projectiles,each one slightly larger than
the last, so hard on the barrel was the powder charge. The barrel was good for
only so many rounds before it had to be changed. Or, at least the liner had to
be changed. Not sure. Must have been a go to Hell rifling machine! The shells
reached the stratosphere, where the air was so thin,the shells could fly
farther with nearly no air resistance. They dismantled the gun, and the Allies
never did succeed in finding it after the war.
Big Bertha was not the nickname for the 800mm Dora rail gun. It was the name
(Dicke Bertha) for the ultra-heavy mobile 420mm siege gun used by Germany in
WW1.
Ps the "Bertha" in the nickname is in reference to the corpulent Bertha Krupp,
of the aforementioned artillery/steel dynasty.
There was a large rail gun the Germans used in Italy, the Gustav. They ran it
out of a tunnel to use it, then ran it back in. Those guns were a big waste of
troops. I THINK I read that they took 2000 men to operate, and had to have a
high ranking officer in charge. For what damage they did to our troops, they
weren't worth the effort.
When the "Big Bertha was first named, Bertha was a young girl in the Krupp
family.
Originally Posted by 9100
The Sharps 45-2.6 was said to launch a 500 to 550 grain bullet from the mid
1200s to around 1300 FPS. The 45- 70 military load was supposed to be 1250 FPS
with a 405 grain bullet, and the 577 martini which is a bottle neck type
cartridge was said to push a 400 grainer (450 gr ? I forget) at somewhere
around 1350 FPS. In the post buffalo hunting heyday, Sharps came out with a
slightly longer cartridge capable of holding more powder thus yielding
slightly better velocities, however diminishing returns along with the
cumbersome nature of such a long "experimental" cartridges seem to have put
the brakes on the longer is better school of thinking.
Originally Posted by Scottl
How does it stack up to the powder? What's the reason that powder is more
common?
Originally Posted by capital7
Some inline muzzle loaders use pellets with a central hole and AFAIK most of
the other pellet and cake forms are either industrial use or to make it safer
to transport. Packed powder will burn or deflagrate but if air space gets
between the granules multiple wave fronts can cause detonation. The cake form
tends to just burn in a shipping accident.
Forgot to answer the second question. Powder is more versatile as it can be
packed into various calibers at different loads where pellets have to be a
close fit to the chamber and load adjustment must be in steps - 1 pellet gives
a certain velocity, 2 give another velocity and so on. AFAIK pellets for
muzzle loaders are only available in .50 caliber.
Originally Posted by capital7
If you could make it burn fast enough. Some solid fuel rockets have a solid
propellant cast into the rocket body. They have a star shaped hole in their
centers to increase burning area that is designed to burn away the inner
points, reducing area as the ID increases, keeping a fairly constant thrust.
These have a burn time measured in seconds, not milliseconds. Whether you
could make it go that fast is debatable.
We were co-typing. That is a partial answer.
Originally Posted by Scottl
Forgot to answer the second question. Powder is more versatile as it can be
packed into various calibers at different loads where pellets have to be a
close fit to the chamber and load adjustment must be in steps - 1 pellet gives
a certain velocity, 2 give another velocity and so on. AFAIK pellets for
muzzle loaders are only available in .50 caliber.
Alright, that makes sense
I'm just guessing, but I'd think you're better off burning the extra powder in
the barrel rather than accelerate it along with the projectile. Assuming it's
spent by the time it leaves the muzzle.
Wesg, we discussed that. The weight of the BP gasses limits velocity to around
1700 FPS. The burning powder is pushing the whole column of gas, which is why
I'm thinking of reversing it so the powder expansion takes place between the
projectile and the breech/gas column.
Once again, read the paper in this link.
http://www.dtic.mil/dtic/tr/fulltext/u2/a203307.pdf
If you get the propellant moving, the resulting leading edge gas velocity is
the sum of the speed and the expansion of the burning fuel. You want to burn
all the propellant in the barrel because it will be pushing against the
already burned fuel instead of only its own weight
I didn't read that the first time. It look like a potential velocity of about
6822 FPS, but this was smokeless powder.
The current tank guns are nearing that, I have no idea how, and however they
are doing it they are getting fantastic accuracy from smooth bores. (Nominal
Velocity: 5,510 ft/sec)
It's not traveling charge though.
Originally Posted by partsproduction
The current tank guns are nearing that, I have no idea how, and however they
are doing it they are getting fantastic accuracy from smooth bores. (Nominal
Velocity: 5,510 ft/sec)
It's not traveling charge though.
The Chinese gun uses a small diameter penetrator with a 120 mm sabot, claiming
2,000 meters per second.
http://www.popsci.com/china-builds-worlds-fastest-tank-gun-then-tries-hide-it
China Builds the World's Fastest Tank Gun, Then Tries to Hide It | Popular Science
I wonder what the propellant is. You could possibly reach a higher limiting
velocity by making a propellant that forms combustion products with a low
molecular weight. You could get things going a lot faster with a hydrogen-
oxygen or methane-oxygen mix. The problems with mixing and getting them into
the chamber would be formidable. The Chinese gun seems to be using a solid
propellant though.
9100
10-12-2016
So, as to black powder velocities, I wonder if anyone ever tried carrying
the charge with the projectile so that freshly burning gasses are added to the
column at the projectile end instead of the breech end where it has to push
that long column of gas? Said moving cartridge might separate at the muzzle.
The aim here is maximum velocity, not accuracy. (Gyrojet, but it did not use
pressure but thrust instead.)
partsproduction
10-12-2016
jabezkin
10-12-2016
calvin b
10-12-2016
sealark37
10-12-2016
partsproduction
10-12-2016
bridgeport
10-12-2016
Forestgnome
10-13-2016
The simple answer to the OP's question lies in the chemical properties of
black powder as opposed to smokeless powder. Smokeless is classed as a
propellant that burns over a short time period of time, producing a gradual
increase in gas volume and pressure. Black powder is considered an explosive,
which releases chemical energy in one violent reaction. This pulse of energy
occurs in such a short time, and produces such a high volume of gas, notably
at one point, that the physical tensile yield values of the projectile and the
barrel are reached before a great velocity is reached. Regards, Clark
GunBum
10-13-2016
The simple answer to the OP's question lies in the chemical properties of
black powder as opposed to smokeless powder.
gwilson
10-14-2016
Thumann
10-14-2016
gwilson
10-14-2016
bridgeport
10-16-2016
So what velocities did they get at max?
capital7
10-20-2016
Probably. Black powder in pellet or cake form has been around since at
least the war between the states and even has a different UN number than the
powdered form.
Scottl
10-20-2016
How does it stack up to the powder? What's the reason that powder is more
common?
9100
10-20-2016
Would a solid type of BP work without the perforated end plate?
capital7
10-20-2016
Some inline muzzle loaders use pellets with a central hole and AFAIK most
of the other pellet and cake forms are either industrial use or to make it
safer to transport. Packed powder will burn or deflagrate but if air space
gets between the granules multiple wave fronts can cause detonation. The cake
form tends to just burn in a shipping accident.
wesg
10-20-2016
partsproduction
10-20-2016
9100
10-20-2016
partsproduction
10-20-2016
9100
10-21-2016
I didn't read that the first time. It look like a potential velocity of
about 6822 FPS, but this was smokeless powder.