Automatic or semi auto Gas rifle

[Boob Raider]

A recent trip to homedepot sparked an idea ..... A tank of methyl acetylene and O2, along with a sort of a CO2 pistol design with a spark plug with a barrel. Do you get the picture. What I mean is to have a CO2 pistol or rifle design and instead of CO2, an O2 balanced mix of methly acetylene and O2 is compressed by the cylinder's pressure and ignited by the spark plug or something similar.
No need to buy ammo ... one could probably cast slugs at home and buy gas at any hardware store. And modifing the rifle to different configuirations shouldnt be difficult, like for a sniper rifle increase the size of the pressure chamber and barrel calliber to .22 cal. So what do you think guys ?

[A-BOMB]

Look around at yard sales, because I remember someone was making .35cal carbide powered rifles. My dad had one put gave rid of it because he couldn't find any carbide.

[Eliteforum]

It's possible to make one, the design would be almost simular if not identical to a spudgun.

The only differance would be it has a rifle stock, and the sheer size of such I thing..

[Boob Raider]

Fuel is not a problem ... methyl acetylene is available in 400 gm cylinders and the O2 in 40 gm cylinders same size though. They are about 12" long, so I am thinking they would make the rear stock (butt), but the problem I am comming accross is the clip feed as I can't quite picture the slug entering the barrel without a leak. :( . Also would the barrel of an air rifle work as I can't get my hands on anyother barrels ..... Its Canada ... I can't even possess (sp?) an air soft with a color marking on the tip of the barrel. Pathetic Canadian laws. :mad:

[zaibatsu]

I think the Germans in WW2 looked at using acetylene-oxygen mixes in mortors. Didn't come to much, as they couldnt find a way to regulate it effectively, which shouldn't be too much of a problem nowadays. But, a sniper rifle? How are you going to make sure you use exactly the same proportions, amount, etc each time, to end up with a good enough consistency? Plus, if you're using an unrifled barrel, I'd say just use BP, its not that expensive in bulk and it would make it more portable.

[Boob Raider]

I can get a rifled pellet gun barrel. What I meant was I can't get the one in which live rounds are fired ...... for that I need a licence and that would cost me about 400$ CD. As fas as the consistancy goes ... I an not taking off more than 10 shots for sniper applications per tank or maybe less depending on the O2 consumed ... I haven't worked it out yet. Also there would be a larger pressure chamber for the mix for extra power .... whose volume I would have to calculate to keep the slug sub-sonic. Anyone know how much energy is transfered to the slug in a revolver as semis and autos absorb a bit of the energy in reloading (I am not too sure if that makes a difference in the muzzle velocity).

[Energy84]

Be careful if you're going to be compressing oxy-actylene mixes together. I've heard that if it is compressed too much (more than 15psi) that it can actually detonate on its own.

[Anthony]

I remember reading and article in an airgun magazine about this guy, who amongst other things, had knocked together an oxy-acetylene powered gun. It was either .22 or .30 and would put a slug through 2" wooden boards at either 100 or 200yds.

zaibatsu's point was that without very precise regulation, you will not be able to ensure a consistant power output shot to shot. Which makes the gun inaccurate as the trajectory of the projectile will alter if it's muzzle velocity is changed. It certainly wouldn't be a sniping tool, but then not many improvised guns are.

I don't think a CO2 gun would work too well as you don't have a combustion chamber. What might be better would be to take a standard spring gun, remove the spring and piston, block off the end of the compression chamber and install inlets for your oxygen and acetylene, as well as installing a spark plug. Projectile loading would be straight into the breach as normal, no leaks or other problems there. The larger the calibre of the gun the better, as you'll likely impart more energy to the projectile, as it's heavier and has a larger surface area for the pressure to push against. A switch to fire the spark plug would be installed in the trigger guard so that the existing trigger blade pushes against it, or ditch the existing trigger and just push the swicth/button directly with your finger.

You'd have to really clean out the gun as the grease/oil in a high oxygen environment might cause an accidental firing.

[Boob Raider]

Would compressing the fuel air mix (like in an internal combustion engine) increase power worth taking the pains (I think it will get too complicated with a piston or are there any other methods) ? Also how much of the energy is transfered to the slug (in %) so I can keep the slugs sub-sonic. The reason I prefered .22 cal is that the pierce class II armour quite easily and also a compressed air rifle (the single shot spring ones) barrel would be easy to acquire.

[Eliteforum]

Perpahs you could rig up something like:

<img src="http://www.boomspeed.com/eliteforum/rifle.gif" alt=" - " />

I don't know how you would connect it to the trigger mech though..

[xoo1246]

Military has been working on gas/oxygen propellants too, it's an advanced topic, it's not as easy as calculation grain burn speed etc.
When you test this, take security measures, many accidents has happen with acetylene. Especially dry gas.

[A-BOMB]

If you are doing this I just saw a set of 5 electrical gas regulator/valves on e-bay yesterday for 12$. So If you unite them with a a couple 555's and a few other componets you can get the exact same amounts of gas each time you fire. I also saw a circuit diagram for a gas regulator circuit on a spudgun site I can't remember it right now but I'll find it and post the link later.

[zaibatsu]

I wouldn't advise compression with oxy/acetylene mixes if you value your life, I think Acetylene doesn't like pressure too much <img border="0" title="" alt="[Wink]" src="wink.gif" /> . Check this page for a diagram of the regulator a PCP uses to ensure consistent results <a href="http://www.airguns.net/reviews/regulators.html" target="_blank">http://www.airguns.net/reviews/regulators.html</a> It would have to be set up in a slightly different way, IE you charge the chamber first using the regulator and then fire.

[Boob Raider]

I was going to use needle valves for that porpose and a 2 ball valves to open gas flow. If I lead the tubes a little into the middle of the combustion chamber rather than keeping them to the walls of the chamber ..... I am hoping it will reduce the back pressure on the non-return valves guarding the pressure/combustion chamber upon ignition so they will last many more shots. :p
So to keep it sub-sonic I have to keep experimenting with it. Ooo I can't wait to get the damn chamber turned on a lathe and get the barrel .... I've got the valves, tubing, fuel etc :D . Oh don't have any slugs though. Does anyone know how to cast FJP's at home with lead and copper sheet or its just not worth it.
Thanx for all the input though guys <img border="0" title="" alt="[Wink]" src="wink.gif" />

[Anthony]

Compression would help, but I can't say how much of a boost it would give. There may be a simpler way of converting a spring gun *and* having compression.

You basically leave the gun as-is with the exception of someway to inject the oxygen and acetylene into the compression chmaber. So you cock the gun, load your projectile, inject the gas and fire the gun as would normally. The stock trigger releases the piston, the spring drives it forwards, compresses the gas mix whilst rapidly heating it to auto-ignition point - compression ignition, just like in a diesel engine.

Recoil may be pretty fierce and the spring/piston may be damaged after prolonged use. On the upside, the recoil will likely drive the piston back far enough for the sear to engage, saving you from having to manually cock it for the next shot.

[MrSamosa]

Am I the only one who sees something wrong with using Oxy/Acetylene?? Look- that stuff burns hot, that's why it is used in welding. WHY do you want to use that in a hand-held spudgun type device? First of all, you risk barrel overheating if you fire more than 2 rounds per minute. This barrel overheating could lead to structural failure in different parts of the gun, most likely at the joints. Why not just use the Butane/Propane/Oxygen mix? That is quite powerful, and doesn't burn nearly as hot as Oxy-Acetylene. If I were you, I would work on maximizing the efficiency of the more common propellants rather than messing with some new, hot propellant.

One interesting idea I saw came from the Nazis' MG-42 Machine Gun. Notice at the muzzle there is a nozzle, like on a rocket. Why not try to employ that on your gun? This could have been mentioned before in other threads, but I don't remember reading it. If you INSIST on using Oxy-Acetylene, try to employ some sort of cooling system on the barrel.

[Anthony]

I doubt that overheating would be a real problem, the ROF isn't exactly going to be high.

I don't think you'd be too succesful casting homemade projectiles, unless you could get hold of a commercial mould, or maybe a swaging kit, then you could do FMJs.

Heavy air rifle pellets would make an idea seal, but don't count on them staying subsonic. .22LR bullets would work if you can get them. 5.56mm, particularly FMJs would probably be a bit too heavy/tough.

[Boob Raider]

Sam like Anthony says overheating is not a problem as the gun will be firing bursts, whereas the torch uses a continious jet. Its like gunpowder firing rounds does heat the barrel but not as much as a pile of gunpower deflagerating. Actually majority of the barrel heating comes from the projectile friction with the barrel. Propane and butane don't pack somuch energy compared to acetylene. I think it due to the tripple bond. If you have ever used an oxy-C2H2 torch, you definately would have heard a sharp, loud sound when turning off the torch, whereas you will never experience that in an oxy-propane torch. Thats one of my reasons. Thanx for your input though, you too Anthony ... It been helpful.
Anthony the air rifle spring compressing the gas idea is really tough on the piston rod but not that much on the spring. I used to fire AP powered slugs ... the forced air was enough to detonate the AP and the slug (made solid with solder) would have enough power to make about an inch deep creater in a brick at 10 mts. The recoil wouldn't cock the spring but would ram the piston shaft hard enough to make it bend after about a 20 shots. I used less than 300 mg if AP.

[MrSamosa]

I remember reading off of some spudgun website, I don't remember which one it was, that if you are even spraying hairspray down the barrel for each shot that you risk the barrel overheating and falling apart at the joints if you try firing more than 4 or 5 rounds per minute. They suggested not trying more than 3 rounds/min. We will have to see with your acetylene gas and the reload times for it. Still, don't try being too adventurous.

And sorry for my bad terminology when it comes to firearms...but could you clarify yourself when you say "bullets" ? Are you referring to the bullet itself, or the bullet along with the casing + gunpowder? Because if you are referring to the casing + gunpowder as well, then overheating the gun risks "barrel cookoff", i.e. the ammunition going off prematurely.

[Boob Raider]

Sam, I almost always use the word slug or projectile. I think what Anthony meant, was slugs too as I already have the propellant(shouldn't this be called projectant for projectile ??) the O2/C2H2 (actually the fuel I'll be using is CH3-CHCH2, methyl acetylene, propyene). Hey Anthony, does the suffix LR mean light rifle ?

LR = Long Rifle (by Zaibatsu)

methyl acetylene is actually CH3-CCH - kingspaz

<small>[ September 18, 2002, 04:25 PM: Message edited by: kingspaz ]</small>

[parabolic]

well, i for one was also thinking of making a butane or propane oxygen mix, rifle. i work for a barrel company so i have no probs in making myself a rifled barrel, but the only thing i would have prolems with is mixing the oxygen and butane/propane together, in order to charge the weapon, i have many pizo igniters on hand so internal spark ignition would not be a problem, just mixing the gases together would be, i also have my boss on hand who is a balsitic expert, so he can help me with balistics and any dangers that i may find., do pulse jet engines work on gas and oxygen, because there must be somthing that mixes them together for that to work surly?

i got planes for making a pulse jet engine, maybee i should have a look :) .

-----------------------
hes using propYne (CHCCH3) not propAne (C3H8)- kingspaz

<small>[ September 18, 2002, 04:23 PM: Message edited by: kingspaz ]</small>

[Anthony]

Yeah, by "bullet" I mean just the projectile.

[Boob Raider]

Hey Para, I was using needle valves preset to the O2/Fuel mix with 2 ball valves controling the main gas supply from the cylinders. Or do I have to use something fancy. Are there any good valves in a furnace (for heating homes), or any other similar source.

[man_o_brass]

I'm not familiar with "methyl acetylene" (my organic terminology is a bit rusty, but welding acetylene is VERY unstable at pressures over about 15 psi. If you tried to pressurize it with an oxidizer, you'd get some unwanted fireworks. Anyhow, if the two are the same thing keep the pressure low. A buddy of mine ran a steel potato gun on oxy/acetylene, and most of the time the spud wouldn't make it out the barrel in one peice. My point is that it has plenty of power at atmospheric pressure.

[AfroFukinPyro]

Oxy-acetylene shouldn’t pose any big problems as long as you keep the acetylene WELL BELOW 15 PSI. As it has been stated, acetylene becomes unstable and unpredictable at around 15 PSI unless it is stored in a special "sponge" cored tank containing a certain type of acid (I forget what kind). This is how the acetylene is stored for welding at around 150 PSI I believe, but as soon as it is regulated out of the tank it is kept below 15 PSI.

If you decide to work with acetylene, keep it under 8 PSI just to be safe. There may be a safer fuel for this application though, one which is safer to use and possibly has more explosive power, yet gives off less

[Boob Raider]

Actually ... like I mentioned earlier the gas is methyl acetylene aka Propyene, CH3-C=-C-H. That =- is a tripple bond. Hydrogen was another gas that packs a lot of punch but is not available easily or generating it for this purpose will be a bitch.

[MoToMaStR]

Hey, thats a really good way to have the chamber explode and send that wooden stock splintering in hundreds of pieces towards your shoulder and neck. Personally,.... from my experinces with oxy-acetylene torches from welding and near accidents Iv had,.. I definatly wouldnt fuck with it. listen to energy84 and zaibatsu dude. oxy-acetylene isnt seomthing you really wanna play with. propane is much safer. Detonation occurs on its own around 15-22 psi,... like satated before and Believe me, air rifle barrels arent ment to handle much more than about 600psi of compressed air/C°2. So your likely to lose body parts while you mess with it. Im not saying dont do it,... but the mix compressed is about as stable as shaken nitro-glycerin. =) Hope that helps make your decesion on building your contraption.

[Anthony]

Good general advice, but I beg to differ on your point about about the pressure handling abilities of the barrels. For a start, many barrels have a wall thickness greater than 5mm. Secondly, they are expected to handle 3000psi for millions of shots in the case of PCPs.

I just think they're a lot stronger than you give them credit for.