exploding capacitor rifle

[edy]

You need a police issued firearms license.
Only certain classes of firearm can be licensed.
For instance, fully automatic firearms are banned.
They can be used for just about anything except shooting humans… Targets, pests, venison back steaks, etc…

Canada is similar, you have to undergo 1st a firearms safety course and optional additional 2nd course for "restricted" firearms. You need also a 3rd hunting course if you want to use them for hunting. Most approved trainers will offer all 3 courses: 1st course is long-guns (e.g. hunting rifles), 2nd course (optional) for restricted (hand guns, semi-autos, etc.) and the 3rd hunting course (optional if you just go to the range to shoot).

You can also buy air rifles (limited to under 500 fps shooting speed) of either 0.177 or 0.22 caliber quite easily, no license needed at all. I think you need to be over 18. When you buy pellets the stores will record your ID as well (they ask for my drivers license and write it in their log books). I have a "spring air" gun called the Ruger Air Hawk with scope. It's a great target shooter, aka "plinker", to practice basic posture, breathing and aiming skills. You can set up a shooting range in your basement if you have the space or at the cottage or any other private field without any concern (there are obvious safety considerations and you need to be smart and responsible even with this, or you or others may get hurt):



I can tell you that with some practice using the scope (I have crappy eye-sight and wear glasses) I am getting groupings of under 1" at 50 feet and that's not even close to the tightness that pros get. The pellets even at that distance are still powerful enough to go completely through various cans, and will pierce thinner wood slats. Definitely you don't want to be on the receiving end of the rifle. But it is a convenient, cheap and easy way to get into target practice and learning about firearms.

Now back to the capacitor-overload-powered "gun". The idea is that when the capacitor explodes, it's contents vaporize and the resulting gas wants to expand and therefore forces out the projectile/bullet. The expansion ratio can't be very great and while it will probably shoot something out of a barrel, it will contaminate the bore and probably damage it on repeated firings. It seems expensive as well considering that an air/spring-gun can accomplish many factors of power greater pressure with an air piston (and also larger expansion ratio) repeatedly with no issues and without contaminating the bore, and no need for electricity at all. Just add pellets (which are inexpensively obtained at about 1250 for around $25) and pump away! Even if you could manage to shoot, crack open your barrel, reload a pellet, close the break-action, aim and shoot again every 15 seconds.... You would be shooting for over 5 hours straight and probably your arm would fall off from exhaustion, for only $25.

With a capacitor gun, I can't imagine how difficult it would be to reload a projectile and the "capacitor" propellant efficiently and consistently, hook it up properly electrically, get the proper electric charge going and have it fire predictably. It would probably be a very complex process that takes time to set up, and when fired will be unpredictable rate and time and power, with pieces of the capacitor flying around inside the bore scratching and contaminating everything in sight. So for anyone wanting a reliable efficient cheap consistent and safe firearm, using a capacitor is going to fail on all levels compared with even the most simple cheap air-gun and pellets, and provide way less power.

Also keep in mind that while I can only get a 500 fps air-gun without a license, once I get a license (1st course) I can own regular long-guns that take actual ammunition (i.e. "bullets") and also air-guns that are much faster.... 1000 or 1250 fps.... compare that to a rifle with regular gunpower ammunition that will be upwards of 2500 fps. Also they are extremely reliable, hugely higher velocities are available and heavier projectiles which deliver way more energy to the target.

I would be much more interested in an electric "rail gun".... NOW THAT IS SCARY and FASCINATING at the same time. I don't think they are going to make something more portable and safe any time soon but here is an example:




Here's another example of an electric railgun but you can see how pathetically slow the projectile is travelling, it even bounces off the glass bulb although makes it shatter.    Even an air-gun pellet would have gone completely through and into the wall behind:



The actual electric rail gun used by the military is a huge beast with awesome firing capability.... Reaches MACH 7 speed and the projectiles are massive. MACH 7 is around 7800 feet per second... compare that to some of the fastest rifle muzzle velocities at around 3500-4500 fps, just a bit over half that speed. The military electric railgun will shoot a 3.2 kg (7 lb) projectile to MACH 7. The .204 Ruger can fire a 32-grain (2.1g) projectile at around 4225 fps. So do the math... E = 1/2 mv^2...

3200g @7800 fps  vs 2.1g @4225 fps. Not taking units into account or figuring out the exact energy, I just want to know purely the ratio... we have 1/2 x 3200 x 7800^2 compared to 1/2 x 2.1 x 4225 ^2, or 97344000000 : 18743156 is about 5193 : 1 difference in power at the end of that projectile between the military railgun and one of the fastest rifles.

[JxR]

is about 5193 : 1 difference in power

Although your ratio is totally correct (and gets the point across fine) because both calculations had the same "errors".  I'm going to be that guy and point out that J = kg(m/s)^2. So your units need some conversions to get the right numbers in Joules.

[edy]

is about 5193 : 1 difference in power

Although your ratio is totally correct (and gets the point across fine) because both calculations had the same "errors".  I'm going to be that guy and point out that J = kg(m/s)^2. So your units need some conversions to get the right numbers in Joules.

Right, so 97344000000 g(ft/s)^2 : 18743156 g(ft/s)^2. 

Ok let's do the proper conversion.

1/2 x 3200 g x (7800 ft/s)^2 compared to 1/2 x 2.1 g x (4225 ft/s) ^2
1/2 x 3.2kg x (2377 m/s)^2 compared to 1/2 x 0.0021kg x (1288 m/s)^2
9040206 J compared to 1742 J.... again a ratio of about 5189:1

Said another way... 9 MegaJoules to 1.7 KiloJoules.

Given that an Asian Elephant ways about 5000 kg, the 5000:1 ratio would be like comparing the weight of an elephant to a rabbit. What would you rather have dropped on you? 

[Stray Electron]

  If you're interested in rail guns then you should go read 'The Moon is a Harsh Mistress' by Robert A. Heinlein.  The numbers are impressive to say the least. A rail gun will never be an effective endo-atomspheric weapon anytime in the foreseeable future due to air friction and the fact that there are efficient ways to project energy. Ex-atmospheric is an altogether different scenario.

  Edy, I'm surprised that you didn't bring up Gerald Ball! What kind of Canadian are you anyway? 

[edy]

  Edy, I'm surprised that you didn't bring up Gerald Ball! What kind of Canadian are you anyway? 

Gerald who? 

Actually I just Googled it now... it's not "Ball" but "Bull":  https://en.wikipedia.org/wiki/Gerald_Bull

I remember this story, it was a long time ago, he was caught building long-range canons for Saddam Hussein government and was assassinated in 1990 possibly by Israeli Mossad agents in Brussels. I see there was a movie made about him on HBO:

https://en.wikipedia.org/wiki/Doomsday_Gun

What a dangerous career to be in! He seemed to have made too many enemies and was purely an engineer for hire without any qualms about who he might be helping, despotic dictators and what-not. When you are in that business you have to make choices on who to work for, and he obviously made the wrong ones.

[Stray Electron]

  I don't know if they ever actually got used or not but in the early 1960s Bull made some cannons for the USN (IIRC) that were supposed to be able "fire" satellites into orbit. They used two 18" naval gun barrels welded end to end.  Bull tried for decades to find a buyer for his ideas, but when he finally did it turned out to be the wrong one (Sadam Hussein) and at the wrong time!

  Just to get this thread back on track, maybe the OP can make some multi-chambered guns (Bull's design); but with exploding capacitors!   

[edy]

  Just to get this thread back on track, maybe the OP can make some multi-chambered guns (Bull's design); but with exploding capacitors!   

Yeah I just don't see how the amount of vaporized gas/residue from the contents of a capacitor have the expansion coefficient to create the kind of pressures needed to accelerate a projectile. If you have no bullet in front of the capacitor in the chamber, you just have gas and pieces of capacitor flying out the gun barrel. It basically acts like a "blank"... making a nice pop sound but probably not very damaging at all as the minute the gases leave the barrel they dissipate the energy in all directions.

If you can place a projectile in front of the capacitor it will need to be forced by the expanding gases out of the barrel. Some experimentation is in order, such as different ratings for capacitors, different sizes, low ESR vs. regular, the amount of current to dump into them and voltage... lots of parameters to determine the best "expansion" options so produce the highest velocities.

One other thing I always wondered was that a typical air-gun pellet is made up of lead. I know bullets can have metal jackets but I have never seen an air-gun pellet other than pure lead. Is there a reason for that? Even pointed pellets don't have much penetrating power because the lead is soft and deforms. If I shout at anything hard, the pellet squashes into a pancake. If something about the same weight as a pellet could be made but harder with the same weight, or perhaps slightly longer to keep the weight similar but still fit the 0.177-caliber air-gun chamber and out of a stronger material (steel), would it not have the same velocity characteristic (given equal mass) but have better penetration?

Could the use of the soft lead be in order to allow a good seal to prevent venting of the pressurized gases around the projectile as it launches through the barrel? I noticed the back end of the pellet has a bit of a mushroom shape and it fits snuggly against the walls of the barrel when you insert it. I imagine as it travels down the rifled bore, the softness moulds the back end tightly against the barrel and keeps the pressurized air from escaping around it. A harder material or jacket might not permit the kind of operation that air-guns require to keep chamber pressures. In a gunpowder-fired bullet the amount of force generated I would imagine is many times higher than an air-gun so even a harder jacket would conform to the bore but there would still be escaping gas around it, just not as much of an impact???


 

[tautech]

All that edy.
Yes air rifles use a cupped pellet that the edges expand to improve the air seal while the head of the pellet is just a good fit in the bore. Also the cup must expand sufficiently to engage with the rifling to spin the pellet to stabilize its flight and maintain accuracy.
Lead has all these advantages that are also used in conventional rifles to a point where heat generated from higher velocities starts to leave traces of lead in the barrel which eventually has major detrimental effects on accuracy.

Modern jacketed projectiles are far more advanced and engage deeply into the barrel rifling with little clearance to the nominal bore diameter for an effective gas seal. Typically the modern projectile is jacketed completely except for the tip.
For higher velocities various gilding metals are used to jacket the lead core and permit much higher velocities to be achieved with far less barrel/bore contamination. Projectile jackets are commonly copper alloys however nickel has been used and even Teflon coatings to reduce bullet friction.
Yet there still is some bore deposits depending on bore finish and velocity.

[james_s]

I really don't see the point, an exploding capacitor doesn't have much energy, it's not really an explosion, it's just gas pressure causing the top to pop off. I have an air rifle that will shoot a .177 pellet clean through a piece of 3/8" plywood, not gonna get that kind of force out of a capacitor popping.

[Stray Electron]

All that edy.
Yes air rifles use a cupped pellet that the edges expand to improve the air seal while the head of the pellet is just a good fit in the bore. Also the cup must expand sufficiently to engage with the rifling to spin the pellet to stabilize its flight and maintain accuracy.
Lead has all these advantages that are also used in conventional rifles to a point where heat generated from higher velocities starts to leave traces of lead in the barrel which eventually has major detrimental effects on accuracy.

Modern jacketed projectiles are far more advanced and engage deeply into the barrel rifling with little clearance to the nominal bore diameter for an effective gas seal. Typically the modern projectile is jacketed completely except for the tip.
For higher velocities various gilding metals are used to jacket the lead core and permit much higher velocities to be achieved with far less barrel/bore contamination. Projectile jackets are commonly copper alloys however nickel has been used and even Teflon coatings to reduce bullet friction.
Yet there still is some bore deposits depending on bore finish and velocity.

   Lead projectiles are only good up to about 1200 to 1500 f/s before lead fouling in the barrel becomes a major issue. That's why nearly all rifle projectiles (other than .22 LR) and many high powered pistol projectiles are copper jacketed. The relative softness of lead projectiles can also lead to feeding and jamming problems, particularly in self loading full or semi-automatic weapons.  That's why virtually all of the military ammunition is fully jacketed aka FMJ, Full Metal Jacket. FMJ is also more or less required by the 1899 and 1907 Hague Conventions.

   There have been numerous attempts to coat projectiles with Teflon, Moly disulphide, nylon and other low-friction coatings but the benefits are rarely worth the very slight improvement in performance. 

   I have used lead air rifle pellets that are electro plated with copper but I can't see that they're an improvement over plain lead alloy projectiles.

   FYI I say copper plated but the bullet jacketing is usually a copper/ zinc/ tin alloy called guilding metal.

[tautech]

Er well yes all that and more.

Lead is often mixed with Antimony to get greater hardness and thereby reduce lead barrel fouling at higher velocities however this limits the styles of lead bullets that can be used, for example the cup based mini ball style used in black powder muzzle loaders, lead/antimony alloys may be too hard to get reliable expansion of the cup.



While lead fouling is an issue with old calibers and the reason jacketed projectiles are now in widespread use, lead fouling in classic and reproduction firearms is a perfectly manageable nuisance.
At one time the bullet styles didn't allow for adequate lubrication but now we have better designed bullets that will hold the specialized projectile lubricants that are commercially available:
http://rcbs.com/Products/Bullet-Casting/Accessories/Bullet-Lubricant.aspx

Therefore with alloyed lead projectiles that use this sort of design lead fouling is a lesser issue than black powder fouling for those that like to shoot these old timers for a bit of fun.

[Stray Electron]

Er well yes all that and more.

Lead is often mixed with Antimony to get greater hardness and thereby reduce lead barrel fouling at higher velocities however this limits the styles of lead bullets that can be used, for example the cup based mini ball style used in black powder muzzle loaders, lead/antimony alloys may be too hard to get reliable expansion of the cup.

[/img]

   LOL. I think that I have that exact mold.  If I'm not mistaken that is the Lyman mold for the .58 caliber Minié ball as used in 1864 Springfield rifles. It's unusual in that it has tapered grooves on the base of the bullet. It was hoped that those would scrap out the black powder fouling that accumulated in the rifle barrels.  I have an original rifle as well.

   You left tin out of the bullet mix.  Antimony is ok but tin is much better and will give you hard bullets, particularly if you chill them when you drop them out of the mold.

[tautech]

You left tin out of the bullet mix.  Antimony is ok but tin is much better and will give you hard bullets, particularly if you chill them when you drop them out of the mold.

Sure, if you want to push lead based projectiles to their max but there's only so much velocity you can take lead alloys to before the centrifugal forces from the rifling twist rate tears the bullet apart in mid flight.

Modern (last 50 years) rifles that spit their loads fast have all had this problem and it's been addressed with better and tougher jackets to hold the projectiles together. Probably the most famous is the .22 cal 220 Swift that was one of the first mass produced calibers capable of consistently exceeding 4000 fps. Still today if the wrong projectile is selected for use in the 220 Swift they will fly apart shortly after exiting the barrel.

[Stray Electron]

Sure, if you want to push lead based projectiles to their max but there's only so much velocity you can take lead alloys to before the centrifugal forces from the rifling twist rate tears the bullet apart in mid flight.

   True but lead fouling in the barrel and failure of the bullet to grip the barrel rifling (called "stripping the rifling") and subsequent bullet tumbling in flight and complete loss of accuracy, occur at much lower velocities than what it takes to make a bullet tear apart so you rarely get to that point.  Years ago we experimented with a full length .300 Winchester Magnum necked down to .25 caliber.  With a full power charge it would rip apart even FMJ bullets. The only bullets that it didn't rip apart were ones made of solid bronze. It was a great round and it would really reach out there and touch something but it really just wasn't worth the work and costs to build a special gun, reloading dies, chambering reamers, etc for that caliber, except for bragging rights. I still have some of the solid bronze bullets but loaded ammunition with those is now considered to be armor piercing and is illegal.

Modern (last 50 years) rifles that spit their loads fast have all had this problem and it's been addressed with better and tougher jackets to hold the projectiles together. Probably the most famous is the .22 cal 220 Swift that was one of the first mass produced calibers capable of consistently exceeding 4000 fps. Still today if the wrong projectile is selected for use in the 220 Swift they will fly apart shortly after exiting the barrel.

   Tell me about it. I bought several .22 and .25 caliber molds but they're largely useless except for reloading .25-20s. Any other useful .25 caliber cartridge is too fast to use lead bullets, unless you're just making plinking loads.

[EEVblog]

Well considering Australia bans guns completely

Err, no, I can go and apply for gun ownership tomorrow. The laws are just very strict.

As for the capacitor, it's got to be bugger-all energy compared to gun powder/explosive. An electrolytic capacitor explodes because the dielectric liquid inside heats up, expands, and bursts out the weakest point (usually the vent hole on the top).
It would be interesting to know how far and how fast a cap would be propelled out of a suitably sized sealed end barrel.

[SiliconWizard]

I really don't see the point, an exploding capacitor doesn't have much energy, it's not really an explosion, it's just gas pressure causing the top to pop off. I have an air rifle that will shoot a .177 pellet clean through a piece of 3/8" plywood, not gonna get that kind of force out of a capacitor popping.

I don't know how much energy though. I have already witnessed "explosions" of electrolytic capacitors polarized in reverse. One was accidental and very close to one of my hands (it was a 1000µF/50V capacitor IIRC and accidentally polarized in reverse with, if I again RC, -12V). It didn't do a lot of damage but I can tell you it HURT and I got a 2nd-degree burn. There was of course this nasty impregnated paper all over the room. The other cases were intentional for "demo" purposes . I just can tell you that if you polarize them in reverse and don't limit the current to a low value, most of them will literally EXPLODE. When treated this badly, the slotted vents are not enough usually to prevent a complete destruction. I suggest people skeptical of this to just experiment! IME, the reverse polarization with enough reverse voltage and a high current limit will lead to spectacular stuff with many electrolytics.

Of course some caps may be better designed than others in that respect.

Also, even though the result can be "spectacular", it usually takes a few seconds to happen. So for a riffle...
It could probably be much faster with very high reverse voltages. If anyone is willing to further experiment...

[EEVblog]

"A government that does not trust it's law-abiding citizens to keep and bear arms is itself unworthy of trust." -- Jeffrey R. Snyder, 'A Nation Of Cowards'

Tautech, if you turn this into a gun rant thread I'll shut it down.
Please keep on topic.

[EEVblog]

Also, even though the result can be "spectacular", it usually takes a few seconds to happen. So for a riffle...
It could probably be much faster with very high reverse voltages. If anyone is willing to further experiment...

I've done a video:


You'd likely need a specially designed capacitor, as lets say you put one down the end of a nicely fitting barrel vent end first so the gas would come out the vent at the sealed back. How far would it have to be from the sealed back wall before it propelled it forward instead of bursting the bottom of the cap that has the seals around the pins?
And then you'd need either really fine wires going down the barrel, or else some form of custom contacts on the sides of the barrel and the contact would have to be good enough but not tight enough to prevent the cap flying out. Sounds like it'll be a bit of a schmozzle.
But of course if you put some sort of projectile in front of the cap and just used the cap as a gas explosion for force the projectile out then you'd have better luck than trying to get the cap to fly out.
But I'd want to see any "capacitor rifle" actually fire the capacitor, else it's a bit lame.

[SiliconWizard]

I've done a video:

I haven't seen this one! Will take a look.

But of course if you put some sort of projectile in front of the cap and just used the cap as a gas explosion for force the projectile out then you'd have better luck than trying to get the cap to fly out.

Most likely yes.

But I'd want to see any "capacitor rifle" actually fire the capacitor, else it's a bit lame.

In that case, I have some doubts. As you said, you'd have to design a proper barrel. And the capacitor would still have a tendency to disintegrate IMO before it reaches its target if that's what you meant. So yeah the capacitor itself would have to be specifically designed for this.

[coppercone2]

gerald bull is a real life goblin from warcraft. anything for some gold. i bet saddam paid him in gold

[coppercone2]

  Edy, I'm surprised that you didn't bring up Gerald Ball! What kind of Canadian are you anyway? 

Gerald who? 

Actually I just Googled it now... it's not "Ball" but "Bull":  https://en.wikipedia.org/wiki/Gerald_Bull

I remember this story, it was a long time ago, he was caught building long-range canons for Saddam Hussein government and was assassinated in 1990 possibly by Israeli Mossad agents in Brussels. I see there was a movie made about him on HBO:

https://en.wikipedia.org/wiki/Doomsday_Gun

What a dangerous career to be in! He seemed to have made too many enemies and was purely an engineer for hire without any qualms about who he might be helping, despotic dictators and what-not. When you are in that business you have to make choices on who to work for, and he obviously made the wrong ones.

[Rick Law]

  If you're interested in rail guns then you should go read 'The Moon is a Harsh Mistress' by Robert A. Heinlein.  The numbers are impressive to say the least. A rail gun will never be an effective endo-atomspheric weapon anytime in the foreseeable future due to air friction and the fact that there are efficient ways to project energy. Ex-atmospheric is an altogether different scenario.

  Edy, I'm surprised that you didn't bring up Gerald Ball! What kind of Canadian are you anyway? 

Let take this from chemical or mechanical back to electrical...

re: A rail gun will never be an effective endo-atomspheric weapon anytime in the foreseeable future due to air friction

The unforeseeable future is almost here...

With current technology, US Navy shown off a rail gun shooting at 5600mph, that is about 8210 feet per second.

The M16 rifle muzzle velocity is 3110 ft/sec, the AK47 2350 ft/sec.  What the USN shown was a cannon so it would be different than rifle.  Looking at another famous gun, the GAU-8/A Avenger 30mm cannon: the one that the A10 Warthog "tank killer" was designed to carry, the muzzle velocity is 3324 ft/sec.

No doubt what the USN shown is a bit too big to put on your belt, but it clearly shown that rail gun can reach meet and exceed the muzzle velocity of chemical explosion driven velocity.  Now they need to shrink it a bit further and make it a bit easier to use and deploy...  Say another decade or two perhaps.

For me, I'd rather jump to direct-energy weapon like killer laser (anti-material) or killer micro-wave (anti-personnel).  Point and cook...

^{USN Video here:}

[EEVblog]

No doubt what the USN shown is a bit too big to put on your belt, but it clearly shown that rail gun can reach meet and exceed the muzzle velocity of chemical explosion driven velocity.  Now they need to shrink it a bit further and make it a bit easier to use and deploy...  Say another decade or two perhaps.

I doubt major reductions are possible for that size projectile, the power requirements are just so massive. IRRC current power systems on existing ships are not enough, only the Zumwalt-class destroyer has the power system capability in place.

[coppercone2]

thats because they got tired of unclogging barnacles from steam water intakes, I don't think other ships were designed with power generation in mind

[EEVblog]

But I'd want to see any "capacitor rifle" actually fire the capacitor, else it's a bit lame.

In that case, I have some doubts. As you said, you'd have to design a proper barrel. And the capacitor would still have a tendency to disintegrate IMO before it reaches its target if that's what you meant. So yeah the capacitor itself would have to be specifically designed for this.

With enough experimentation I think it's likely possible to get a cap flying out at a decent velocity, but it's going to be messy. More like a shotgun