Does Anybody Know....

[Foto Joe]

Does anybody know what the terminal velocity of a bullet is in a Black Powder gun. Specifically a revolver or even a rifle.

It stands to reason that since the combustion of BP does not accelerate with an increase in pressure that the velocity of a projectile fired from a BP gun would have a finite velocity. Therefore an increase in the amount of powder will eventually reach a point that velocity is no longer affected in a positive manner.

 

[Oldnamvet]

There is a guy over on the muzzleloadingforum.com who would quote a formula for how much black powder would burn in a given barrel volume which sounded reasonable. Finally it was checked and found that if you continued to increase the powder charge, the velocity continued to go up. Put in more powder and the velocity still went up. The people checking didn't continue since it may have damaged the gun. When questioned, it was found that an old guy had told him this value (something like 11.5 grains/cubic inch of barrel volume) and he had declared it a formula with the guys name on it. So it was not something that had been experimentally determined -- or there was no documentation on it. About the only possible use of the formula would be to provide a reasonable starting point for working up a load if you had no other information.
As to the answer to your original question - I haven't a clue.

 

[ofitg]

Looking through the Lyman Blackpowder Handbook, the highest muzzle velocity I can find is 2505 ft/sec.

.36 round ball, 43-inch barrel, 70 grains of FFFg.

I'm not sure if that answers your question (?)

 

[Foto Joe]

Looking through the Lyman Blackpowder Handbook, the highest muzzle velocity I can find is 2505 ft/sec.

.36 round ball, 43-inch barrel, 70 grains of FFFg.

HOLY C%$#P!! I didn't think it would be that high. That's 1,115 ft. lbs. of impact energy if the RB weighs 80gr., that would be impressive. I'm guessing that if it were in a Lyman Black Powder Handbook, it would have been at least chronographed by them at some point in time.

Anybody else want to take a stab at what terminal velocity with BP would be??

 

[[email protected]]

That is correct. The old way was to use as much powder in grains as the
ball weighs. In my 58 that would be 325 grains!!

 

[mykeal]

I'm not sure what you mean by terminal velocity. In aerodynamics terminal velocity is defined as the speed at which drag equals the weight of the projectile. It has nothing to do with the amount of force used to initially propel the projectile.

The 'Davenport formula' alluded to above suggests that there is no limit to the speed attained by a bullet, although there is a point of diminishing returns at which the percentage increase in powder used results in a lesser percentage increase in velocity. There is significant disagreement about the veracity of the Davenport formula, although test results suggest there may be some merit to it. To date I'm not aware of any tests that have found a point where increasing powder results in no increase in velocity.

I would think that point, if it exists, would be a terminal acceleration, not terminal velocity.

 

[ClemBert]

Here's some useless information for ya....

Figure that a battleship could fire a 2700 lb projectile at around 2500 fps. I've read where 4000 fps is about as fast as anyone has launched a projectile before giving up for faster speeds. Doubtful that we are talking about pistols or rifles....human sized ones anyways. I know, I know...I'm useless but non-the-less interesting facts.

....but....it was black powder that launched the projectiles down a rifled barrel.

 

[zimmerstutzen]

The Davenport formula has to do with powder efficiency and target shooting. Anyone that tells you that more powder always leads to more velocity is just plain out to lunch. The Lyman Black Powder Handbook First edition has a hundred pages of tables for calibers, barrel lengths, velocities, etc. If you compare the increased muzzle velocities per ten grain increments of powder, the velocity increases do drop back and become neglible at a point. Where they start dropping off, is the point of diminishing returns. In a 50 cal, 28 inch barrel with 2fg, that point of diminishing returns is about 100 grains for a round ball. Few people exceed that point even for hunting.
The diminshing returns occurs because the powder burns slower than the ball travels down the bore. At a certain point in increasing loads, there is more powder than can be consumed before the ball exits the muzzle. The excess powder is used up in muzzle flash and part of it may be expelled unburned.
I can tell you that fouling seems to increase as loads exceed the point of dimishing returns.


The Davenport formula for that same 50 cal barrel is less than the point of diminshing returns. It would be length times pi times radius squared or 28 x 3.1417 x .25 squared x 11.5 grains or 63.23 grains of powder. As a starting point for finding a most accurate 50 caliber target load that is pretty good. It is not a hard and fast rule and certainly has less application when used in very large calibers or small ones. Alot of other things also affect powder efficiency such as the rifling configuration and the patch ball seal

 

[zimmerstutzen]

For instance according to Lyman's Black powder handbook, 1st ed, page 112, a .498 round ball fired out of a 28 inch barrel from:
80 to 90 grains gains 144 ft lbs
100 grains to 110 grains gains 121 ft/lbs,
120 to 130 grains increases 89 ft/lbs,
130 to 140 gains only 30 ft/lbs.

That is hardly a straight line energy increase.

at 100 yds the curve is just as pronounced

80-90 grains the 100yd increase is 32ft/lbs
100-110 grains the 100 yd increas is 32 ft/lbs
120-130 grains the 100yd increase is 30 ft/lbs
130-140 grains the 100yd increase is 9 ft/lbs

again, not a straight line increase.

the point of diminishing returns for velocity increases is when 110 grains is exceeded.
the point of diminshing returns for ME is 100 grains
the point of diminishing returns for 1ooyd energy is also 110 grains.

See a pattern?

 

[Jim K]

It is not clear to me what information the OP is seeking. "Terminal velocity" is the velocity of the bullet when it stops at or in the target; it has nothing to do with the powder used. As for "finite velocity", any moving object has finite velocity; the opposite would be infinite velocity, which is not possible.

As for a point where an increase in the powder charge does not equate to an increase in velocity, that is true of any powder. It is not due to the limitations of the powder as such, but to the fact that a reasonable length barrel is too short to burn all the powder. At some point, unburned powder will be expelled from the barrel to burn outside the barrel and its potential force wasted. (The characteristic "flash and BOOM" of a heavily loaded gun is caused by just that and demonstrates that to the shooter making noise is more important than efficiency.)

Jim

 

[Oyeboten]

There is a lot of grey area.


Many other Powders or possible propellants exist which are very close to Black Powder, or which are different forms of Black Powder which were not normally used in Firearms, but, which possibly could be used, or added to regular BP in some proportion, to gain FPS when all else is equal.

Some of these would certainly require much stronger Guns to test or try, as well as to study and think carefully about their known properties first.

I do not have access to them now, but, I have a few, thick, heavy mid to latter 19th Century formularies which had many pages of different kinds of Blasting Powders and Flash Powders and Rocket Powders and related, and these were all mostly special Powders closely related to BP.


Some of these would blow up any regular Arm if tried.


But, broadly, they could also be regarded as being in the Black Powder family...and, intermediate versions probably could be made or tried, if one wanted.


Thus, who knows what speeds a BP fired projectile could have?


Even if needing a Gun built for "that" propellant to get away with it!

 

[Martyk]

It sounds like the OP is looking for how fast a BP bullet will travel by using XXX much powder and when do you reach a point where the addition of more powder will not achieve an increase in velocity of the bullet.

I'm not sure that it exists.

 

[Foto Joe]

Oh brother, look what I started....

Let me explain the original question. I'm one of those people who happens to like worthless trivia, sometimes it's not so worthless. This question, even though I might have worded it somewhat incorrectly has some merit.

I would think that point, if it exists, would be a terminal acceleration, not terminal velocity.

mykeal is right, I'm looking for "Terminal Acceleration. Thanks for the clarification.

With smokeless powder, let's use Unique, when the powder is ignited the pressure immediately begins to increase. As the pressure increases the speed at which the powder burns increases (I'm sure there is a mathimatical formula for this but I'm not that bright). The initial pressure increase is the primer detonation. Without getting into the effect of supersonic shock wave and its effect on the projectile, suffice it to say that given enough smokeless, the muzzle velocity of a given projectile will eventually reach a point at which the gun can no longer withstand the acceleration of said projectile and fail because the projectile can no longer accelerate fast enough to relieve the pressure inside the vessel (chamer/barrel) and it goes kaboom somewhere other than the muzzle.

Now, since Black Powder does not burn at an increasingly higher rate with an increase in pressure, it stands to reason that at some point the muzzle velocity of the projectile will cease to increase with the addition of more powder. Remember during this discussion that my intent was to keep the subject to the guns "We" use. Navy guns and artillary are a whole 'nother matter.

Why do I need to know this? I was looking for a laymans answer to a physics question. I certainly am too cheap to use that much powder in any gun. Keep in mind that this forum is read my hundreds who never post. They are new to BP shooting in general and they learn a bunch from even the most ignorant of us (I being one of the latter). I guess that's why I posted the question in the first place, I like to learn stuff and there are some pretty smart people reading and posting here.

Ignorant people like myself will forever continue to be that way should we never ask questions and regard the answers from those not quite so ignorant.

Speaking of trivia, "Did you ever wonder exactly how deep the ocean would be, if sponges didn't live there?"

Sorry, I couldn't help myself on that last one.

 

[ClemBert]

Figure that a battleship could fire a 2700 lb projectile at around 2500 fps.

So you must have really appreciated my useless input.

Question: How many pounds of BP does it take a battleship to hurl that 2700lb projectile at 2500 fps.

Answer: A lifetime supply for you and me.

(somewhere around 600 lbs)

 

[junkman_01]

The US Navy no longer has any active battleships, but when they did, they used BP only in the powder bag closest to the breech. The rest of the charge was smokeless powder.

 

[zimmerstutzen]

I'm not so sure that bullet velocity reaches a critical point before a barrel rupture as a certain amount of pressure, which of course depends on metallurgy, wall thickness etc.

To make matters even more obtuse. The method by which barrel pressures were measured and stated has changed in the past 40 years. In the past, pressures were stated according to "copper units of pressure" Which I understand was somehwat imprecise to measure anyway. More than a few oltimers, told me that a muzzleloader barrel should be able to withstand "about 20,000 CUP. with the average load running around 10,000 to 12,000 CUP" If you check the tables in Lyman's Black Powder handbook, you will find that moderate round ball hunting loads run in that 10,000 to 12,000 CUP neighborhood, although some pressures as high as 15,000 CUP are reported with very heavy loads For instance, who would be so suicidal as to use 170 grains under a 45 cal PRB. Generally conicals bullets having heavier mass, created higher pressures with the same powder charge.

Muzzleloaders have been known to fail and rupture from average loads under short started balls. This means that the ball wasn't seated on the powder but left a few inches from the muzzle and the burning powder still developed sufficient pressure to cause a barrel failure. In such cases, the ball was either still or slowly moving and a rupture still occurred.

 

[ofitg]

I read somewhere that the upper velocity limit for a conventional firearm was around 5000 ft/sec with smokeless powder..... it had to do with the rate of expansion of the gases behind the bullet.

I have never read what the theoretical upper limit might be with black powder. The Lyman Blackpowder Handbook lists a few loads exceeding 2000 ft/sec (yes, they were chronographed) but I can't find anything faster than 2505 ft/sec.

 

[alsaqr]

I think that you are interested in determining the point of diminishing returns. Toby Bridges conducted a test using 50 grain equivalent Pyrodex pellets. The gun was the Savage muzzleloader. Three pellets gave the 250 grain saboted 250 grain Hornady XTP bullet a muzzle velocity of 1,955 fps. Four pellets with the same bullet gave a velocity of 1,930 fps: Recoil with four pellets was horrible.

 

[Oyeboten]

Yes...the Bullet/Projectile can not accelerate faster then the speed at which the elastic pressure-front of Gasses bearing against it are accelerating, anyway...


So whatever the limits of speed for that, the limits of speed for the Bullet/Projectile, must be less.



But in practical terms, Standard Small Arms of the Black Powder era, were designed for the comfort and utility of persons useing them, and, of the general circimstances of use....of course.


It would be interesting to have a 4 Foot, 7 Foot, 10 Foot long Barrel Rifle, Percussion, and use a very large Powder Charge, and various ( very well lubed ) Bullets, and Chronograph the results.

Or do what those guys did with testing commercial Ammo in various Barrel lengths - start off with a fifteen Foot Barrel, a massive Charge, a Heavy Bullet, and cut off an inch at-a-time, Chronographing the same Charge and Bullet for each Shot...and plot it on a Graph.

 

[arcticap]

If the combustion rate of black powder is controlled by granulation then ffffg would produce more velocity than fffg. And isn't there a 5F flash powder or something similar that would be even faster?
There must be reasons why no one advocates loads using the fastest granulations.
Why even try to duplicate smokeless performance with black powder?
Many of the fastest baseball pitchers in history had a tendency to be wild and not able to consistently throw strikes.

 

[Oyeboten]

Flash Powder ( What Photographers used to use ) will Blow up a Gun very readily.

Do not try it!


I do not think Foto Joe, or I, are trying to 'duplicate' Smokeless Loads.

We are just interested in BP and learning more about it, especially learning more than the blind rote of "just do this" with no understanding.

In both our cases too, we have Arms made during the BP Era, for which we would prefer NOT to load and fire Smokeless Cartridges.

There is a whole lot of not much for published info on BP in many ways, pressures of various Loadings, Velocities and conditions, etc.

Onr pretty well has to do their own research to find out.


Fun to learn, fun to wonder, fun to think, fun to try things one had thought out.


I am getting good as or better Velocities in my BP Loadings of Metallic Cartridge, than most boys and girls are getting with smokeless for same weight Bullet and a comparable Arm.

This is just a nice incidental to the larger explores and trials toward understanding more about it.


Not trying to compete with Smokeless, nor to out-do it...just curious about what BP can do in Metallic Cartridge Revolvers...and, because it is fun in many ways, too.

 

[arcticap]

I do not think Foto Joe, or I, are trying to 'duplicate' Smokeless Loads.

The original question was about how fast black powder can push a projectile.
How else can that be determined without trying to begin to replicate smokeless loadings and performance?
At some point the envelope begins to get pushed.
In all honesty, 4F powder or such would need to be used to complete the experiment.
The question isn't only about testing very safe loads, it's about determining a theoretical maximum velocity load and seeing what velocity would result.
AFAIK packing too much powder into a bore can result in a fizzle at some point. Someone has described that happening to them when they packed a barrel full with black powder and it doesn't necessarily blow up the barrel.

 

[Foto Joe]

Oyeboten hit the nail on the head!!

I'm just looking for a theoretical maximum. By asking the question, I think we're all learning something or at least it's making us think. I'm also interested in just how fast smokeless could push a projectile, I'm just not interested enough to ask.

The day I fail to learn anything will be the last day of my life.