Improvised .22 Handgun

[Yorki_pyro]

Have I been here long enough to make a thread yet? If not please don't kill me!

I know the idea of improvised handguns has come up before, but never in this form.
The idea i have is to take a normal break barrel air rifle or pistol and convert it to fire .22 rimfire rounds by first stripping it down and silver soldering a firing pin to the front of the piston, then ream out a chamber (as the rifling on an air rifle starts too close to the breech for a shell to fit in without modification to the chamber.) then to fire jsut place a shell down the barrel, cock the rifle and when the trigger is pulled the piston whacks the firing pin into the cartridge, simple.
The idea of this is to get better accuracy than a zip gun.
What do you all think?

[Dave the Rave]

Yorki p.

You´re talking about some .17 air guns rigth ? because at my Country the air guns are all 4.5 mm, and must be chambered and reamed to fit one .22 - when it´s done, the barrel becomes so thin that can´t hold the pressure of the shot.

If it can be done on the .17, I´m not sure, as I´ve never seen one of those weapons around here, but there is one problem, the piston moving against the cartridge will build pressure, as if the reguular air gun, how overcome it ? And how stop the firing pin to perforate the case of the ammo ?

[zaibatsu]

Dave the Rave:

From what he's said, I'm assuming he's from the UK. There are plenty of cheap .22 break barrel air pistols around there, mostly from China. The barrels are plenty thick enough. But you just know that the piston-firing pin will burst the primer, those things would hit it hard.

I guess you could stop pressure build up by drilling some holes in the chamber that the piston fits, but you'd still have the problem with the power it's going to hit with. You could lighten the spring, but then you increase lock time.

[NickSG]

I suggest you use the airgun for parts, since to me it wouldnt be worth the trouble modifying it to fire .22RF.

.22 rimfire rounds have a primer on the outside of the rim, so your firing pin would have to strike the outside rather than the center. I dont think there would be any room in the first place to get the rim to stay in place when you close the gun.

The .22 shell will push itself back as the explosives in it burn, which could easily damage the inside of the gun. I could be totally wrong here, but I just think you would be better off using the gun for parts.

Zaibatsu- Which barrels are strong enough to withstand .22 pressures? The CO2 or piston powered air rifles? My friend has an old .22 CO2 pistol from when he was a teen that he doesnt need anymore, and I was wondering if I could make any good use of the barrel.

[zaibatsu]

NickSG: Buy a cheap chinese air rifle in .22, I don't think a CO2 airguns barrel would be a safe thing to use. I'm sure it would take a couple of .22LR shots, but I wouldn't use it.

I just had a horrible thought: the .22 air pistols are a break barrel design, and the breech locks up tight against the front of the piston chamber wall. Just dropping a .22LR in and shutting it up quick would crush the rim :eek:

[Yorki_pyro]

You could vary the force of the firing pin by either leaving the piston seals in place to form a cushion of air when the piston moves or remove the seal and drill holes in the piston face to increase the force of the hit.

[xperk]

as most airguns will use some sort of rubber seal attached to the barrel, this seal (depending on the make the barrel) often resides in a grove cut in the barrel, so the 'chamber' will almost surely not be sufficiently strong to sustain the discharge.

I believe a safer design would be to use a .22 airgun barrel sleeved with some seamless tubing.. I have posted this in another thread - so sorry for crossposting. I do so anyway because I feel that what you propose would not be safe.

The firing pin hole in the airgun is likely to be much too large for the firing pin (at least 4mm.) so there would be a real risk of a blow-back towards your eyes (if shoulder fired).

You could take the inner parts of the airgun, the stock, the trigger system and the barrel and apply these to a Sten Gun like design.
This way you could potentially build up the chamber area with tubing to achieve a fairly strong construction.

--

oh yeah otherwise.. the break barrel - slam shut firing system- earlier proposed by zaibatsu could actually be triggered by the main spring if the safety system on the trigger was removed - would make for quite a surprise! :)
I has a cheap airgun once without a safety, it doubled as a switchblade baton

[Yorki_pyro]

xperk, Do you mean a risk of the cartridge case popping and blowing back through the trasfer port into the cylinder or blowing the whole thing to bits? Also I could remove the rubber seal and fill the groove full of weld metal if everyone agrees that this part is too weak.

[xperk]

I think both scenarios are likely:
- firstly the cartridge might backfire if the firing pin hole is not properly sealed, anyways if you use a centered firing pin for at rimfire cartridge the thing may misfire. In which case someone would have to remove a now distorted and jammed live rimfire round from the chamber, not a holiday scenario...
- secondly the chamber walls of the airgun barrel are simply not meant for the abuse. Welding the grove/rubber seal embedding may work as a filling material. However it doesn't solve the main concern about wall strength of the chamber.
The average airgun barrel is around 17 mm. max. OD this in theory presents plenty of wall thickness, when compared to a .22 rifle. However! the metal quality between the two is different.
Most airgun barrels are made with cold drawn steel tubing, whereas firearms are made with rifle steel.

[Yorki_pyro]

I never said I was going to use a centered firing pin, and also the length of the firing pin could be adjusted so it can not pierce the cartridge. I think that the barrels are strong enough just from the thickness like you said and I'm prepared to risk a cheap rifle being blown up, not like I'm going to have it near me for the first shots. Also, what damage would a backfire do apart from blow gas into the piston chamber?
Damn temptation to make weapons is going to set me back by a good few £££.

[xperk]

The theoretical test firing by remote sounds like a sound idea :)
I don't mean to be a nag about this but..

The centered firing pin issue could be a problem due to the hole from the compression chamber to the barrel being aligned (most likely centered), so you would need to weld that up - and drill a new hole off-center..

The backfire (ok yezz I am a sissy) could be a problem if it was shoulder fired - the gases could travel backward into the compression chamber and blow out through the various openings. This could result in anything from a burnt triggerfinger to a lost eye if the gasses and debris came out near your face.

In any case good luck with your project, I would advice strongly against using the barrel if not reinforced.

[Dave the Rave]

Yorki P, I don´t think that the risk is worth. Really, from the barrels I´ve seen, it´s made from poor steel and can´t hold the pressure, and the piston will surelly burst the primer. The best scenario the gun will not fire, the worst the gun will fire an jet of fire at your face.

The idea of reinforce the barrel can work, but then you will have to enlarge the back of the barrel, to fit the rim of the ammunition, to prevent it from beeing fire by the closure of the gun. As your rim will be inside the barrel, you will have to devise an way to extract it, wich will be dificult, as the expansion will force the case against the walls of the barrel. The pressure of the gun can be lowered by the drilling of the chamber, but it will result on an weapon fragile.

Maybe using only the barrel and improvising one small firing pin, one nail inside ob a piece of tubbing, powered by an small heli spring ?

[zaibatsu]

Instead of saying this and that why don't you just tell us what you can do, what equipment you've got, and we'll have a think Yorki.

[charger]

Converting an airgun to fire rimfire cartriges has already been discussed, although not in detail in the silencer section of improvised weapons. It can be found here. http://www.roguesci.org/theforum/showthread.php?t=587&page=4 the differences in the barrel diameter is an important thing to take into consideration. A barrel that is too small, combined with the poor quality of most airgun barrels (they aren't made for the higher pressures of cartriges) would almost definately lead to disaster. If you still want to try this, I would without hesitation agree with xperk with remote test firing.

[Bigfoot]

My first zipgun was taken from PMJB Vol 2, made from 2 sections of 1/8" pipe and coupler. Chisel-ground bolt for the firing pin, surgical tubing. Test-fired from the hand (yeah, I know, dangerous). No powder residue in rear pipe, no rupture of cartridge base. Barrel was modified to fit the cartridge by epoxying a thin steel tube inside, then filing chamber to size with chainsaw file.

I suspect that a well-used (worn) .22 air barrel would be fine. A new one, I wouldn't use. In your shoes, I'd use the trigger mech (maybe), the stock and barrel, and redesign the entire receiver.

Just my opinion added to my experience.