Countermass Weapon

[Setharier]

There has been some talk about effective recoilless/countermass launcher. As far as I have theoreticized it, the basic construction parts would be 1.5-2l drink bottle and a plastic/metal pipe the bottle perfectly fits.

The idea is to obtain a 1500mm pipe inner diameter of 95-100mm(the exact diameter of the bottle must be confirmed) made of pvc or alternatively, metal, which would perhaps be more durable. This pipe would be then drag-coated with several layers of finest mesh glass fiber throughoutly. In the middle at 500mm length of there would be double- or even triple layer of glass fibre coating. The purpose is to actually make the device stand pressures that allows 2-4kg projectile to be thrown several hundreds of meters away for being effective.

In the case of making recoilless launcher the double-triple layer of GF must be coated at the end of the launcher, not in the middle since the propellant is at the very end also.

The projectile would be made out of plastic drink bottle 1.5-2 liters of volume. The bottle acts as a shell of the grenade. The bottle must not fit perfectly in the barrel(althrough lesser free space is always better) because the bottle will be saboted with wet paper sabot around the etiquette space and this way it will be perfected into the pipe and tightened. When the paper dries it will shrink a little and stamp itself to the bottle. The paper can be treated with vax to minimize the friction.

The bottle needs a tail for stabilization and it will be most likely much easier to do than rifling. This part of the device is still to be perfected but using gluing, lead-through the bottle's bottom and equivalent methods it will be working. The tail could be made of metal(molded or welded from pieces), plastic-resin-glass fibre - method or from wood.

In the bottle there can be loaded about whatever wanted. KE ammunition would be somewhat waste of material so some kind of explosive charge comes in question. Explosive, shrapnel, incendiary, flash, even HEAT can be considered as working and plausible loads. In the front at the screw plug there will be the impact detonator that could be adjusted duty/off-duty by screwing it as the real ones are used. To the very top of the plug shall be placed striker plate which leads through the plug striker rod to a primer, commercial or self-made, which ignites primary/booster that detonates the main charge when the striker plate hits the target. For example an emptied shotgun cartridge filled with ETN or some of the commercial stable-enough primary material that is detonated by the primer hit by the striker rod.

The countermass can be used or left off, considering the needed amount of propellant by that. Countermass weapons are obviously less noticeable due to the missing backblast and the needed propellant can be adjusted more better. Only the recoilless weapons have usually longer pipe and the propellant is inserted at the very end of the gun. Both recoilless and countermass weapons are recoilless if balanced correctly. Countermass uses literally the countermass balancing the back-force from the projectile, but recoilless uses the backblast as a very-short-timed rocket jet to boost the weapon torwards the projectile and thus the jet and projectile force neutralizes each other.

The countermass can be made of about anything that weights equal the shell does. Even a bag filled with water goes fine. First the idea of the countermass is to be something that will minimize the danger caused behind the gun. Placing sand-filled bottle as a countermass will eventually cause the shell and countermass fly both nearly as long, other goes to the target, other goes stright on your mates. The real guns uses some sort of fibre stuff that is packed with glue or something and when fired, it will spread out the pipe and lose it's speed nearly instantly. I would personally prefer using water-filled bags.

The propellant used in the cracker bag / spam jar launcher is few grams of black powder. It is sufficient enouh to bring the shell tens of meters away. When actual power is needed, one must use larger amounts of black powder or then just move up to the nitrocellulose. The propellant would be fitted between two plates perfectly fitting in the pipe. The powder could or even should be packed up into some sort of cartridge to avoid the granules leaking off or even igniting due to the friction caused by the loading of the gun. The paper used packing the powder can be itself made of or coated with something similar. The plates placed both sides work as the propelling ends for the countermass and the shell and they will push both out the pipe.

Ignition is something that must really be perfected. There are about two methods. Using Piped Ammunition Units that can be ignited electrically and are both easier and safer to use in the action or just simply installing piezo lighter in the place of trigger and wait a second to have the powder cath the fire.

The Piped Ammunition Unit is simply an plastic pipe which outer diameter is same as the launcher's inner diameter. In this pipe would be packed the shell, the propellant charge and the electric fuse and a countermass, sealed from both ends. In the middle there would be metal touch surfaces placed correctly leading into the propellant where has been pulled nichrome wire. In the launcher would be installed metal plates in the middle inside the pipe that will come in touch with the surfaces when the PAU is loaded in the launcher. When fired, the trigger switches the power on, causing nichrome to ignite and leading the ignition of the propellant.

So much for it, not it has been told :) Naturally this wasn't originally my idea.

[-=HeX=-]

Well, there is an existing thread on this so a little search would have gls... Someone even posted a photo of his recoilless weapon there. Are you actually going to try build this or is it all just theory? I considered one for a while but decided against it because of lack of time. If you can build one, then I may try again. The ideas you have are good, for countermass use a load of plaster powder and it will just puff into dust. Nice work though. I will draw some diagram later.

[FUTI]

countermass with sand was old style solution and it makes wide and long exclusion zone behind the operator - easy to make. Recoilless one is more recent approach which still make problems - more complex to build, less trouble for the comrades to watch out but still I wouldn't advise shooting from room or building... backblast will burn your back :-P. "New" approach for me is use of "cold" launched RPGs. Well less muzzle flash I guess, but does it mean also less recoil? It seem to complex for amateur build in my opinion.

[Setharier]

I might be in way of realizing this countermass weapon. Some time ago I just had an image of pipe that shots out stuff to both directions. Now I have an image of enforced pipe that has determined and acquirable and if-working really considerable stuff inside it. Shooting an mass-filled spinning "projectile" that has look of elemental 2nd class made space rocket model spam jar with biscuits flying somewhere behind it up to 75 meters sounds too ordinary. Shooting an ordnance-filled fin-stabilized charge up to several hundred meters away accurately is something that makes me working hard for the goal.

Yep, the recoilless is based on the backblast itself as the counter-booster that neutralizes the recoil force. I wouldn't fling it just as easy, the boost intensity must be balanced, otherwise the gun will jump into your face or act as a very-short-burntime-rocket itself. Personally I keep countermass more, even much more easier to do, althrough recoilless wouldn't be worrying with the overpressure so much.

Using PIAT-style spring launched projectile weapon is another story then. I was researching many years ago "trick the gunlaw" - rocket launcher and was very interested in PIAT, but came in conclusion one should purchase real PIAT or make hell of a work building one himself. Finding a spring equivalent to PIAT for being capable of throwing shell over a hundred meters away and still being loaded by one man is difficult. Ten out of ten of springs I collected were far too strong for used anything else than damping a car.

[Setharier]

Not willing of making a new thread instead I talk about this impact detonating shell construction here.

I was recently speculated myself some HEAT ammunition workup. The basis is once again a 2 litre bottle where is added a tail end for stabilization, 12G shell w/ primer and spring-strained striker head, copper cone over 100mm of diameter and an explosive charge of 0,5-1.5kg made of PETN, RDX or "poor man's RDX", ANNM.

The detonation system is the point of concern. I was wondering of using electric system but found out that it could be potentially hazardous even to handle since only few centimeters of striker movement would initiate the charge. So I came idea of chemical detonation, using detcord initiator. The detcord would be pulled stright through the copper cone OR at the side of it, the front head ending up to the emptied 12G filled with cast ETN and the bottom end ending into the main charge. When the shell impacts on target, striker blows the 12G primer, launching few grams of cast ETN and initiating the detcord, leading detonation into the main charge ending up to EFP. This is actually the most simple impact initiation system I have invented this far and as long as the detcord actually detonates, it would be possible using even so insensitive energetics as ANFO, althrough being not even nearly as powerful as about any other material.

There is a risk of detcord detaching on launch and it will be necessary to attach it into the 12G at least. Secondly if detcord is stuck in cast ETN there is risk of crystal crack detonation if detached on launch.

One of the greatest concerns are on the shaped cone relation on detcord, mostly of that about detcord would ruin or make ineffective when detonating through/at the side of it. Would a copper cone 4mm of strength be destroyed or made ineffective when detcord of 10g/m detonated at the side of it?

When using more larger detonation charge of 0.5-2kg in weight, could it be possible to use "offical" shaped cone construction as projected at here:
http://upload.wikimedia.org/wikipedia/commons/f/f0/Obus_501556_fh000021.jpg

Or have I misunderstood that picture in sense the "front cone" is actually a metal jet guide instead of the actual jet material?

http://img412.imageshack.us/img412/2273/27278963to0.png
http://img133.imageshack.us/img133/1342/73009425si1.png

[Jacob Kell]

Interesting way to make a cheap and easy disposable single-shot launcher that could be stocked in greater quantities for urban guerilla warfare, without having to bother searching for thick steel tubes. But, I wander what else could be used instead of fiberglass, which is very toxic and possibly carcinogenous? an inch or more of ordinary polyester mesh impregnated with epoxy, maybe?

[fluoroantimonic]

I like your idea very much, but I see a few problems.
Getting that thing to have any accuracy at all might be a an issue. If you wanted just frag, chemical, thermobaric warheads it would be a different story, but with those shaped charges you're going to have to have some real accuracy, and that's could be a major challenge. Also I wonder how well a soda bottle would hold up the that much compressional force and acceleration? Maybe if done right it could work, but why not make the projectile out of PVC or ABS pipe? It would be much tougher. I think you'd want to use metal pipe for the barrel, PVC wouldn't last long at all..

According to the little ballistics calculator I have a projectile weighing 3kg with a muzzle velocity of 100m/s and a drag coefficient of 0.25(guesstimate) will drop about 4 meters over 100 meters. That's acceptable I guess.

Assuming the projectile resides in the barrel for .01 s (about 0.5 m travel), that means it would require an acceleration of 10000m/s^2.

For a 3kg projectile that means 30000kg force, over a 10cm diameter area would require a (theoretical) average pressure of 381kg/cm^2. So realistically the barrel should handle 10000psi at the very least.

At 40000psi tensile epoxy/fiberglass, that would require >2.5cm thick walls to achieve a good margin of safety. It's a pretty rough calculation though, really (remote!) testing is the only way to know.

Since BP makes ~40% of its mass as gas at about 33g/mol, theoretically it would require about 2kg of BP... DBSP makes 100%gas at about 27g/mol, requiring 600g in theory. Might be overestimates though.. still that's a lot of powder.

I wander what else could be used instead of fiberglass, which is very toxic and possibly carcinogenous?

Not really, it's used in a huge variety of everyday things... I think it would probably be the best option here.

It's late, I'm going to sleep.

[Setharier]

The picture beneath at my last post features readily-packed ammunition in a PVC-pipe shell. That device is supposed to be pushed into the gun itself, shot and the pipe-shell then discarded. The recoilless featured in here is not an single-shot weapon, instead of that an multi-purpose reusable weapon. At least that's what it is supposed to be. :D

I have faced the problem at the strength of that ammunition. If made out of plastic bottle stright, it will most likely fail immediately after leaving the barrel since joints will break up.

http://img352.imageshack.us/img352/4284/30311188zy4.png
http://img370.imageshack.us/img370/7619/52418094va9.png

There I have proposed crimping an metal sheet pipe used in ventilating around the device from the front crown to the back at the Fin piece.

This inertia-detonated shell includes an 1.5-litre bottle with bottom sawed off and another 1.5-litre bottle headpiece placed into there. At the front there will be 12G full of zirconium powder. The bottom headpiece has 12G with primer filled with cast ETN for PETN main charge. The bottom headpiece is fitted in with resin and the fin part. In the Fin system there will be metal pipe of 10mm where a rod weighting some several hundred grams is inserted having striker pin at the head of it and a spring between the primer and the pin. Around this device is fitted this ventilating pipe and it is crimped at the front tightly and at the back tightly as featured with heavy black line around the system in the picture 2.

The latter picture misses the saboting paper ring.

This ammunition is then placed into PVC pipe where the propellant, ignition wires and a countermass are as well and the heads will be coated with plastic foil to prevent water entering the pipe. This system is featured in my earlier post at the very bottom picture under the launcher itself.

Making device like this can't be impossible since many armies use similar constructed, althrough single-shot countermass weapons. Panzerfaust 3 is a pretty good example.

Concern on that accuracy, pressure and strength is real. Glass fibre is all but toxic, it just makes your hands shy like hell if handled without good gloves because of the microscopic glass shrapnel :)

For the drag coefficient one can do no much if flechettes are not in use. Only way to avoid it in practical is to increase the velocity of the ammunition.

Althrough can those pressure calculations be made stright like that - if you counted in we have countermass weapon instead of conventional cannon which indeed takes all the pressure force into it's walls, then, but I have lived in understanding that recoilless and countermass weapons strain much of their propelling energy into the projectile and countermass/anti-recoil boost, not to the walls of the weapon itself. The pipe acts only as kind of nozzle that projects the energy in two ways and by my physical understanding(very little :D) the pipe handles only the difference off the projectile and countermass.

Example our army's countermass weapon has wall thickness only of few millimeters and the whole thing actually weights under ten kilos and it spreads out death at velocities up to 250 meters per second with 3 kilo warhead.

[Jacks Complete]

Nice thread.

You'll want to re-design that detonation tip design, though. Both of them are effectively useless.

The first design will simply not fire the (hopefully blunted) nail straight, as the tip will likely hit at an angle (the armour will be sloped, even if you lob the thing onto the target) and so it will either break off and go flying, or it will hit off center, doing nothing useful.

The second design is even worse. For that to work, you'd have to hit a point just right! The base of a shotgun cartridge is smooth metal, and so your shot will glance off, causing the inertial system to do nothing at all.

If you want to use the first design, you want to use a steel tube to hold and steer the tip of the nail, and a rubber boot to try and ensure some grip when it hits something.

If you want to use the second design, use a rubber boot on the cartridge, to try and stop it glancing off the target.

Personally, I'd go for a HESH design. Slap the explosive on hard, then explode it, blowing spall off the inside. (Unless you are shooting at something that has a spall liner, in which case, good luck, as a simple shaped charge like this won't even hit, let alone disable it!)

[Setharier]

All suggestions that improve the idea are more than welcome. I would like to hear more about that "HESH" design. Technical specs are from heaven :)

For new (at least in this thread) ideas one could be the technique used in naval mines. There an spike was filled with explosive some sort of and when ship hit the mine it detonated. Similar exploding spike could be screwed at the top of the bottle shot. Doesn't matter in which angle it hit, all is matter that the projectile lands on something head-first and the spike snaps. When packed into the PVC-shell risk of accidental explosion is quite low. Filled with cast primary or pri-sec median like ETN-primary mixture it could be somewhat effective, in theory at least.

[Jacob Kell]

You can make a simple and reliable inertia based system with ordinary matches. A thin aluminum tube, a piece od iron bolt machined to fit in (I use improvised drill-lathe), paper tube that fits snugly, with safety match strike surfaces epoxied inside (at the beginning of each striking surface there is a glued piece of smooth paper on which match heads will lie, so there is no contact between striking surface and match head) A bundle of matches is made, epoxied at the tails, and inserted few mm into the paper tube. A small plastic or paper ring is glued then at the same side of the tube to prevent matches moving backwards. I use a very thin food packaging plastic foil for a small blackpowder container that fits loosely inside paper tube with striking surfaces, it catches fire easily and propagates it to whatever charge is used. Now, since I use this for my bow launched grenades at New Year, I never bothered to find weak springs to hold striking bolt in place so it doesn't detonate prematurely, although for something stronger it would be necessary. I fired hundreds of grenades this way, and if made patiently and carefully it is very reliable.

[Alexires]

Have a look at the ammunition used in the 66mm LAW (http://en.wikipedia.org/wiki/Image:M72_1.gif).

KISS is the way to go.

The best that these can do is 30 degrees from the armour. And less of an angle and it wont fire. Realistically, a 66mm is only useful against things with practically no armour (think cars, walls, people, jeeps). It will not be very effective against a LAV 25 and you can forget about tanks.

It might be possible to use piezoelectric ignition instead of some kind of mechanical device. Have a piezoelectric in the head of the projectile, run a wire from there to the base of the shaped charge (see the 66mm LAW projectile) which then ignites from there. Some kind of hard plastic cap/aluminium will prevent accidental ignition from dropping the bloody thing.

Have a secondary fuse from the end of the propellent to the charge so that even if you miss/bounce off, there is a chance it will go off near something.

What do you think about that, Jack?

[slarter]

Alexires,

The M72 LAAW has a 'Graze Sensitive' fuze which incorporates a secondary firing system using a 'cocked striker' (basically a firing pin under spring tension) that will function the warhead if it hits any where other than on the Piezo in the nose. The LAAW will also punch a hole clean through a LAV-25.

With the A2 model they went to a precision shaped charge liner to improve penetration. They are up to the A9 model now. Most of the later modifications were to enlarge the rocket motor for increased range and there are now three different warheads: a straight taper shaped charge, a trumpet liner shaped charge and an EFP warhead. All are extremely effective against anything with less than 3 inches of armor. I've seen the warhead from an A2 static fired through 8 inches of RHA.

The biggest problem with them is that when they fail to detonate on impact they can be functioned by the slightest movement. They are coming back into widespread use as the AT-4 is overkill in Iraq and Afghanistan and is to heavy and bulky for most soldiers to lug around in addition to all of the other BS thay have to carry.

[Alexires]

Fair enough, slarter. I just gave the stats as they were given to me. By very effective, I mean punch a hole the size of my fist through one side and out the other. It may very well fuck up a LAV-25, but if the shaped charge isn't pointing directly at the personnel then you might not score a kill.