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Author: Subject: Gun design
gregxy
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There is a website homegunsmith (or something like that) that has all kinds of information. The site is more about metal working than chemistry however. These people make fire arms that are works of art.

A couple years ago I wanted to try smokeless powder in my black powder pistol so that I would not have to clean it each time. I carefully worked through the internal ballistics to make sure it would not blow up. In the end you use about 1/5 the weight of smokeless as you would for black powder. However I found that the smokeless I was using would barely burn at pressures that are safe for a black powder pistol. The gun would fire, but there was a bunch of unburnt powder left in the barrel. My pistol and the charge I used, was designed to work at 5000-10000 psi where as the powder (for a 9mm cartridge) at ~30000 psi. Burn rate is proportional to the pressure.

nitro-genes
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Hmm yeah, this would also mean that a real standardized setup I mentioned earlier isn't possible, as the operating pressure is determined by both gun design and propellant type. Not really into guns and propellants as they are illegal here, but what actually makes that blackpowder can't reach the same velocity as NC based propellants? Energy content is lower, sure, but could you design a rifle that operates at really high pressures by changing several design features? Would peak chamber pressures become limiting in this case or is there a max. burn rate with increasing pressure for blackpowder? I've seen burn rates mentioned between 1300 and 4000 fps, but does this translate to the theoretical maximum projectile velocity? IIRC, much higher muzzle velocities can be reached with blackpowder when used in hydrogen-piston driven light gas gun designs... So is it also the composition of the gasses produced? Just curious what would be the theoretical maximum projectile speed for blackpowder.

[Edited on 21-6-2016 by nitro-genes]
Hennig Brand
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With extreme overloading reasonably high muzzle velocities can be obtained with black powder, but it is very inefficient and much less than what can be obtained with smokeless propellants. Here are a few points I think are correct. I will have missed some good points I am sure.

1. Black powder combustion products are less than 50% gaseous or more than 50% solids. Smokeless propellants generally produce nearly 100% gaseous products.

2. A large portion of the energy released when a propellant burns is used up accelerating the combustion products, not just the bullet.

3. Black powder is not a molecular explosive/propellant and also has filler material such as the large potassium atoms as part of the oxidizer KNO3, so even with excellent milling reaction rate/burn rate can never come close to a molecular explosive with almost 100% gaseous products like NC or NC/NG, etc.

4. More hydrogen atoms which are about 1/12 the weight of carbon atoms so for a given weight of propellant will produce more gas volume and energy/heat. This is why candy propellants (sugar and KNO3 rocket propellant) are much more powerful than black powder propellants......more hydrogen so more gas volume, also much more heat of combustion. Hydrogen's LHV (lower heating value) is about 120 MJ/kg, while carbon's HHV (higher heating value) is only 32.8 MJ/kg.

5. Much higher energy content for smokeless propellants.

6. Ideal and normally nearly complete combustion reactions with smokeless propellants.

7. The velocity of the bullet/projectile can never be more than the escape velocity of the gases produced.

8. The effect of pressure on burn rate allows smokeless propellants to achieve much higher pressures and velocities and is very controllable by controlling particle/grain shape and size as well as composition. The effect of pressure on burn rate is very limited (relatively) with black powder.

9. The tremendous energy release of the nitrogen-nitrogen triple bond.

10. Fouling or solids build up in black powder guns causes all sorts of issues besides just being inconvenient and a righteous pain in the arse. Increased friction results in loss of energy and muzzle velocity, loss of or at least variable accuracy, corrosion damage to barrel and other gun components, etc, etc.

Note:
It is a myth, from what I understand, that smokeless propellants necessarily produce higher pressures than black power. Smokeless propellants can easily be made to produce the same or even lower pressures than black powders.

[Edited on 23-6-2016 by Hennig Brand]

"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
OneEyedPyro
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From what I've read the increase in burn speed in relation to pressure is much less dramatic if not non existant after a certain point with black powder, this gives a high tolerance for differences in confinement and increased charge weight.

Many smokeless powders however will continue to exhibit a positive feedback effect to much higher pressures than with BP, this can cause pressures to spike exponentially even with relatively modest differences in confinement or charge weight.

Back in the musket days it was common practice to load several musket balls at once or use double charges of black powder in muzzle loaders, despite this catastrophic failures were uncommon.

Today it's common to see modern guns fail catostrophically even due to comparatively minor things like bullet set back .

[Edited on 23-6-2016 by OneEyedPyro]
Hennig Brand
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Black powder can certainly reach fairly high pressures when confined (ex. black powder pipe bomb), it just doesn't produce nearly as steep, or normally as high, a pressure curve when driving a bullet as smokeless propellants can (the time factor is very important). The barrels on black powder handguns are relatively long in most cases even when designed to be used with fast burning black powder.

There is a great deal of hype and fear mongering surrounding smokeless propellants in my opinion. From the time NC was first dissolved in a solvent, dried and cut into flakes to be used as propellant most of the dangers and unpredictable characteristics were eliminated or nearly so. Burn rate and pressure can easily be accurately and precisely controlled with smokeless propellants in a proven firearm with proven/suitable projectiles. If you have a severe restriction or the bullet is too large for the bore pressure can rise to dangerous levels yes. Use common sense...start low and work up to a suitable load. From the bit of experimentation I did there are often indicators that chamber pressure is getting a bit too high. This is only useful if a small load is tried first and gradually increased. It depends on the type of gun though.

[Edited on 23-6-2016 by Hennig Brand]

"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
Bert
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Smokeless powders (and different granulation of black powders!) are so widely variable that you should not even try to generalize peak pressure vs.time or guess the suitability of one or the other for an application.

Observe the below data, particularly for "Trail Boss". TB is marketed specifically for supposedly low velocity loads in black powder era cartridges.

Pick a propellant. Check the data, do not guess.

Rapopart’s Rules for critical commentary:

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Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).

Hennig Brand
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Very interesting, and an example with a 500gr projectile makes it more pronounced. You make a good point about reading the data carefully. Since the work has already been done for us the data provided could be used to reverse engineer a very similar propellant in terms of composition (mainly NC & NG content) and grain shape and size. By picking simple propellants with simple grain shape and few burn rate modifiers it should be possible to approximate the propellant fairly well.

"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
AdamAlden
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Anyone remember those boxes of bullets that hook up to helicopters? the box is filled with barrels which are filled with bullets making it a solid structure of bullets and propellant. It is the most efficient state of ammo storage. I've had the idea to make smaller versions that can be attached to a hand held platforms. This would make it very easy to reload and produce a fire rate beyond conventional fire arms. Of course the accuracy of the bullets at the back of the barrel would be more accurate with high velocity if the ammo boxes where filled to max capacity.
AdamAlden
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If you have smokeless gun powder and want to alter the way that it burns I would try dissolving some in acetone and then solidifying it to create a different grain. You could also mix some regular gun powder and see what happens.

[Edited on 24-6-2016 by AdamAlden]
Arg0nAddict
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I used to build and sell salute cannons 1/2" thick 6" x 6" base 3 layer fillet weld to secure a 3" dia. solid round stock 7" tall bored to 1.5" that way the walls were 3/4".

I always said these were not meant to fire a projectile because the steel used was mild steel molybdenum alloy (not typical cannon steel). Never fails though some idiot tried to fire a lead ball and basically made a you know what. I made \$ but realized people cant follow instructions. I was nearly sued but I proved his negligence because their was a signed waiver and instructions.

I suggest not firing something that looks like that... I was scared to fire my little dick cannon.

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nitro-genes
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The muzzle velocities for the trailboss powder do seem about the same as for the blackpowder ones indeed, that seems something to remeber, muzzle velocities say nothing about peak pressures apparently. Just curious but how did you estimate the pressures produced, acceleration of the bullet in the barrel or something?

You guys are right of course that the pressure exponent of nitrocellulose is much higher (making it more unpredictable) than for BP, although I haven't seen any data on this for BP. Maybe likely though it is somewhat similar to KNO3-Sugar propellants, which reach a plateau in burnrates with increasing pressures, so really high pressures cannot be reached. Don't know burnrates for powdered KNO3-Sugar mixtures and catalysts added, but could in theory and with some tweaking (and maybe some catalyst added) powdered KNO3-sugar indeed make a decent propellant?. Or maybe golden powder? The latter it is used as ejection charge in pyrotechnics and has a decent burnrate unconfined, but never seen it as rifle propellant. Surely some of the "preppers" out there must have tried these. Would seem relatively more safe unconventional bullet propellants to test than chlorate based ones in any case.

[Edited on 24-6-2016 by nitro-genes]
Hennig Brand
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 Quote: Originally posted by nitro-genes You guys are right of course that the pressure exponent of nitrocellulose is much higher (making it more unpredictable) than for BP, although I haven't seen any data on this for BP. Maybe likely though it is somewhat similar to KNO3-Sugar propellants, which reach a plateau in burnrates with increasing pressures, so really high pressures cannot be reached.

Black powder is simply a physical mixture of fuel(s) and oxidizer(s) and can never be as consistent in propellant properties as a molecular propellant like NC.

Any high performance/powerful "tool" has the potential to be very dangerous in the hands of the uneducated or careless. Unpredictable?.....I wouldn't qualify it as such, but there is certainly a lot of potential for disaster if it is not understood and respected. Black powder isn't in the same league at all.

IIRC, you are correct about the burn rate plateau being reached quickly for black powder. The limits for smokeless propellants are extremely high, basically as far or farther than you would ever want to go when used as a propellant.

With great power comes great responsibility!!!

[Edited on 26-6-2016 by Hennig Brand]

"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
ecos
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it seems i have a miss-understanding. I still can't believe that deflagration happen for the BP ! how can they grantee high burn rate not detonation ?

I thought to try something to make sure if detonation will work or not.
I made 200 mg of acetone peroxide and put them in a tube and then added a ball bearing. I used a candle to heat the tube while I am far away.
a big bang happened and the ball bearing broke a wooden sheet placed at 10 m away.
I know that acetone peroxide shall never be used since it is very sensitive material but I wanted to see if detonation will have the same effect or not.
My conc, there will be a peak pressure due to detonation but since the ball bearing is moving slowly relative to the formed gasses , this will make the pressure decrease very slowly !

the metal tube is still in a good shape. I don't see any cracks in it.
OneEyedPyro
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ecos. I really hope you're joking here

High explosives are not a suitable replacement for propellents. You are going to maim yourself or worse if you keep doing moronic shit like this! Putting TATP in a steel pipe is just Darwin award material.

No gun in history has used a propellent that detonates and there is good reason for this, if no expert in history thought it was a good idea what makes you think it is?!?
You obviously have no idea what you're playing with here.

The pipe may not break from a single 200mg detonation of TATP but mark my words, it will break with repeated use and if you're anywhere near it when it does you could be seriously injured.

[Edited on 26-6-2016 by OneEyedPyro]
Fulmen
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 Quote: Originally posted by ecos I still can't believe that deflagration happen for the BP ! how can they grantee high burn rate not detonation ?

500 years of empirical evidence not good enough for you?

It doesn't matter if we can explain it or not (we can), we still know through centuries of trial and error how BP behaves.

We're not banging rocks together here. We know how to put a man back together.
PHILOU Zrealone
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A detonating material in contact with a bullet or canon may deform them or scatter them.
The peak pressure is not smooth but very sharp...see a shaped charge (SC) or an explosion forming projectile (EFP) effect and modus operandi...the metal behaves as if it is a playdoh/a liquid.

1°) Your spherical bullet may be compressed and be stuck into the canon generating a detonating pipe bomb canon...
2°) Your bullet may decide not to follow the canon and pierce it from the side as a long scratch generating a random shoot
3°) Canon scharpnels may go any direction but the target (the bullet cares for it eventually)
4°) Your candle design is far from safe even if you run fast and far....

Even if far away and under cover/protected an EFP fragment can kill you and pierce metal shielding...

You are thus playing the slutty russian roulette...sooner or later it will get you...just a mather of statistics and experiment repetition.

[Edited on 26-6-2016 by PHILOU Zrealone]

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nitro-genes
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As long as there is a residual force acting on the bullet it will continue to accelerate, however pressures drop quickly in the barrel as the volume of expanded gasses in the barrel increases, until it reaches some equilibrium or leaves the barrel. This is different from a rocket in which exhaust gas velocities are independent from the speed of the rocket, which is why we can reach space. So what if you could somehow fire the propellant in stages, like a rocket, along the barrel, it seems you could increase muzzle velocities? How efficient are propellants anyway, is there much heat loss for example. I fired a rifle at a commercial range few times, and the barrel does tend to get pretty warm after a few shots, is this mostly from friction energy loss or heat conductance?. For a combustion engine efficiency is about 35%, has anyone ever calculated this for a rifle? Could you seriously reduce the pressure exponent for NC by pressing (can it be deadpressed?) it as one solid block using hydraulic press, than having a very large chamber and a small extremely long barrel (enough to allow all propellant to be burned inside the barrel) would you find max velocity possible for NC using rifle?

[Edited on 26-6-2016 by nitro-genes]
Metacelsus
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The "rocket" concept reminds me of the gyrojet (https://en.wikipedia.org/wiki/Gyrojet).

As below, so above.
ecos
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Thanks a lot. I understand now your point regarding a peak pressure that shall be kept almost constant inside the barrel.
a detonation spike is not a right thing as i understand.

so how can they grantee that the gun propellant doesn't detonate?

I think the powder is confined in the casing and this would be detonation ! this is not a free burning .
OneEyedPyro
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How fast an explosive deflagrates is not directly related how easily it will undergo DDT.
It comes down to variety of factors. I'm sure someone else can explain it more elequently and thoroughly than me so I'll just let them

When a gun fires the pop you hear is simply a release of pressure much like popping the cork on a bottle of champagne, completely unrelated to detonation.
Hennig Brand
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 Quote: Originally posted by nitro-genes As long as there is a residual force acting on the bullet it will continue to accelerate, however pressures drop quickly in the barrel as the volume of expanded gasses in the barrel increases, until it reaches some equilibrium or leaves the barrel. This is different from a rocket in which exhaust gas velocities are independent from the speed of the rocket, which is why we can reach space. So what if you could somehow fire the propellant in stages, like a rocket, along the barrel, it seems you could increase muzzle velocities? How efficient are propellants anyway, is there much heat loss for example. I fired a rifle at a commercial range few times, and the barrel does tend to get pretty warm after a few shots, is this mostly from friction energy loss or heat conductance?. For a combustion engine efficiency is about 35%, has anyone ever calculated this for a rifle? Could you seriously reduce the pressure exponent for NC by pressing (can it be deadpressed?) it as one solid block using hydraulic press, than having a very large chamber and a small extremely long barrel (enough to allow all propellant to be burned inside the barrel) would you find max velocity possible for NC using rifle? [Edited on 26-6-2016 by nitro-genes]

I won't try to answer everything in detail, but here are a couple of the most important points to consider regarding smokeless propellants & burn rate & pressure profile/curve. I already posted this before in the bullet propellants thread (link included).

The following was taken from "Ammunition General" (TM 9-1900):

"Burning Action.Unconfined nitrocellulose propellant burns relatively slowly and smoothly but, when confined, its rate of burning increases with temperature and pressure. In order not to exceed the permissible chamber pressure of the weapon in which it is to be used, the rate of burning of the propellant has to be controlled. At any given pressure, the rate of burning is proportional to the propellant surface free to burn. Therefore, propellants are made into accurate sizes and definite shapes."

http://www.sciencemadness.org/talk/viewthread.php?tid=22649&...

[Edited on 30-6-2016 by Hennig Brand]

"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
ecos
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for confined burning with the increase of the temperature and pressure this might lead to explosion as happen in rocket motors.
isn't it the case for BP as well ?
Hennig Brand
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The point is that burn rate and pressure are very much controllable and predictable for those who know what they are doing. The human factor is where most (all?) of the unpredictability comes in. Maybe the skill and attention to detail required is above what most are willing or able to obtain. I think there are many who participate at Sciencemadness that have the required mindset and skill level to do it safely however.

"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
camerican
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 Quote: Originally posted by ecos Thanks all for the info. I really appreciate it. I am convinced now that chlorate is a bad option for guns. I will try to use ammonium nitrate since it is easier to find (fertilizer) or I will make BP. [Edited on 8-6-2016 by ecos]

If AN was used, wouldn't all the sensitizers and fuels leave deposits on the barrel? I am thinking of stuff like aluminum particles that escape combustion, chunks of Al2O3, soot, etc.
chemrox
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Is it possible to make a .40 subsonic load that would still make enough pressure to operate the pistol recoil-loading mechanism. You can tell from the question I know little about ballistics and firearm terminology. (I do know what a lower receiver is) ;^)
CRX

an added question- I just did a search for "wetted NC". Wetted NC is used for ammunition. What is "properly wetted nitrocellulose?" How is it made from NC?

[Edited on 6-9-2016 by chemrox]

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 Sciencemadness Discussion Board » Special topics » Energetic Materials » Gun design Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues