material choice for gun barrel, chamber

[bobo]

I am finally:p going to make a gun, since I have now access to a metal workshop. In my country, firearms are haram and everything will have to be made from scratch or scrap. Besides, this is the whole goddam point, making stuff from scratch.

I suppose I start out with single-shot, maybe to incorporate a magazine when it works. My caliber of choice is a .22 because those are easy to get black market, and seem to have so little force that catastrophic mishap seems unlikely.

I have a limitless supply of 12mm steel bars and a few 16mm steel bars. Of course I can obtain every type of bar needed if these are not right.

My questions to the more experienced tweakers and gunsmiths are:

1. which outer diameter do I take? Is is bigger = better (but heavier)?
2. is it OK to use a 6mm bore for the barrel? or should I order a 5.8mm bit? 5.7mm?
2b. is there a minimum length to the barrel? Obviously, ít will be a short barrel since I'll have to drill it.
3. how many shots can you expect from a gun like this before failure and what be failure be like?
4. do I bother with 'rifling' in a hand gun?
5. should I think about refilling .22 cartridges with stuff that is entirely home made including tips?


And for the alternative backup plan. A single shot shotgun that can be fed with cartridges that I also will have to prepare by myself.

1. Which thickness for the barrel in this case versus the diameter of the shotgun shell?


If good comes out of this, I promise some pictures and plans.

[tomu]

For .22 lr cartridge any steel will do. Even cheap construction steel will have the necessary yield strength to withstand the pressure of a .22 lr. The .22 lr develops a max. pressure of about 1800 bar which translates to around 180 N/mm2 (Newton per square millimeter). Construction steel has a tensile strength above 300 N/mm2 * the yield strength is about 235 N/mm2.

*( I had to make a correction here due to a mistake inmy vocabulary, I mistook yield strength for tensile strength SORRY!)

To 1.:
I wouldn’t go below a wall thickness of 3mm better 5 mm for a .22 lr barrel but I wouldn’t want to exceed a wall thickness of 10 mm (e.g. in a simple rifle). Of course I‘m not talking about high precision competition rifles here obviously.

To 2.:
The bullet diameter of a .22 lr is 5.68 mm so I would choose a 5.6 - 5.7 mm drill bit. And I would step drill my barrel, start with a 3 mm bit and after that drill with a 5 mm bit next take a 5.5 mm bit and after that I would ream it to correct size. If you could ream it to the correct diameter take a 5.6 mm drill bit and measure the bore if it is anything above 5.65 mm I would leave it below that finish with 5.7 mm bit.
To 2b:
The minimum length would be the cartridge length of 25 mm and you won’t gain much by exceeding a length of 450 mm.

To 3.: Can’t answer that for obvious reason.

To 4.:
Do you have the equipment to rifle a barrel? My guess is no. We are not talking about building a competition gun here. For a self defense pistol were the shooting distance is mostly below 5 m I wouldn’t even think about to take the pain and rifle my own barrel.

To 5.:
Out of curiosity I once tried to reload fired .22 lr shells it is a real pain in the ***. The results are as unreliable as you can get it. I used scraped of amorces for the primer pocket and black powder as a propellant.


The pressure of a normal 12 gauge shotgun shell is about 800 bar so it’s even lower than that of a .22 lr. As above I wouldn‘t want a wall below 3 mm better 5 mm.

[teshilo]

You want maximize or minimize thick walls of barrel? Maximize: for use various rounds with various action and gas pressure in barrel.. minimize: for light and disposable use...

[iHME]

I read somewhere that 1,5mm would be enough for .22lr. I'm personally building a bolt-action single shot .22lr pistol of my own design. I'm going to use a 16mm high tensile bolt for the barrel and thus I'd have about 5mm wall thickness so it should be enough. And if one wants to read about good sources for suitable steels for firearms the Bill Holmes books could be a valuable resource.

[Alexires]

Of course, everything here is theoretical, isn't is guys?

*shakes head* Remember to write that it is theoretical, as you wouldn't want some government agency getting the wrong impression that you would think about doing something illegal, or haram as you put it, bobo.

[a3990918]

To 4.:
Do you have the equipment to rifle a barrel? My guess is no. We are not talking about building a competition gun here. For a self defense pistol were the shooting distance is mostly below 5 m I wouldn’t even think about to take the pain and rifle my own barrel.

I agree unless you just absolutly need/want to have a rifled barrel. I haven't seen them in a while but use to you could buy barrel liners for replacing the bore of a shot out barrel without having to purchase a new barrel.. Just drill the barrel out to the manufacturers spec. Apply something like a bearing adhesive to the insert and install. A little trimming up and cleaning up and viola, new rifling. Would of course also work with a smooth bore you want to rifle.

[tomu]

I have a hunch that he can't lay his hands on barrel liners or barrel blanks, so it's fruitless to discuss them. He is talking about drilling his barrels from steel bars, my guess is he wouldn't do this if he could get a real barrel.

Btw. barrel liners could be bought from Brownell's.

May be he could get hold of an old air gun with a 5.5 mm barrel, he could make use of this. But personnely I would not want to waste it on my first try to make a gun.

[a3990918]

I have a hunch that he can't lay his hands on barrel liners or barrel blanks, so it's fruitless to discuss them.
Btw. barrel liners could be bought from Brownell's.


Yes, I understand that due to regulations barrels can be illegal, but are there restrictions on barrel liners?? Anybody?? I wouldn't think so since in and of themselves they do not costitute a firearm component.

Also, there are several plans on the internet for building simple rifling machines.

[kaiserbill]

Yes, I understand that due to regulations barrels can be illegal, but are there restrictions on barrel liners?? Anybody?? I wouldn't think so since in and of themselves they do not costitute a firearm component.

Also, there are several plans on the internet for building simple rifling machines.

There are many countries where owning any component for a firearm that you don't have a licence for is illegal.

Looking at P Luty's info on expedient gun barrels made from seamless tubing, for .22 the tubing he suggests comes with a 2mm wall thickness.

In fact, for the far more powerful 9mm parabellum cartridge, the tubes he recommends have wall thicknesses of between 2.5mm and 3.0mm. I have not yet built his designs so I cannot comment on safety or integrity.

[kaiserbill]

Just measured the barrel thickness of a friends Luger M90 (Browning HP clone).

The barrel wall thickness is 2mm.

[tomu]

Yes, I understand that due to regulations barrels can be illegal, but are there restrictions on barrel liners?? ...


At least there are some european countries where buying barrel as well as barrel liners requires a license.

Depending on the yield- and tensile strenght of the steel you could even go below a wall thickness of one millimeter for a .22 lr. But personally I wouldn't consider it as save and sane especially when more than one shot should be fired from the gun.

Luty shrouds his improvised barrel with set rings (is this the right term for those rings?) to certain length.

[bobo]

well first of all. thanks everyone, especially Tomu for the useful comments.

My steel bars are scrap of unknown quality and as such I'd like to be safe rather than sorry with thickness. Of course, if inspection would reveal the signs of wear instead of a sudden failure then I'd feel safer playing with it.

The prospect of government agents taking action against me seem slim since roguesci would need to reveal my IP and besides, I am not a terrorist just a civilian who hates the strict firearm laws.

The main point is that I want to make a firearm that requires only an archaic lathe, some scrap steel and some toy parts to produce a lethal and concealable weapon. Indeed, for academic purposes only (and publication on the internet) given the fact that I am perfectly allowed to obtain a firearm for sporting purposes and match grade ammo. Legal means that police can show up at any time to check on your weapons, though, so for self-defence, legal firearms are worse than useless here (unless the whole country collapses).

My plan is now to make the weapon with four main parts, pen-gun design. It should have a barrel and the part that locks with it (whatever its name is in english). These two parts are connected by thread, so to load the gun it has to be screwed on. There is a thin tipped firing pin in it and a powerful spring behind it, unsprung just like the spring in a ball-point. All these parts can be disassembled and assembled quickly. I guess I'd make a piece that is interchangeable with the barrel itself, but with a pencil tip in it, so that it looks like some heavy duty mechanic pencil:D

A little tidbit of information: in the Netherlands, white powder is obtainable without the actual permit (of course an organic chemist can manufacture this and leave no trail at all but to do this right takes a lot of skill). In Germany, alarm gun ammo can be obtained there that can be used as the cap (Luty describes this process in the expedient ammo book) for caps. Professional reload materials are outside permit and OTC. Bullet tips are easily obtained. This means that clandestine ammo can be made from OTC parts, in a quality exceeding the factory quality if one is an experienced reloader.. of course the scrap parts gun would be so inaccurate that the quality of ammo is a moot point.

If I go the way suggested by Tomu, I'd take a 5.7 drill bit. The 5.7 size makes it suitable for factory ammo. However, how realistic is it to manufacture our own ammo at basically ANY caliber, including the unsuspicious 6.5mm caliber (aka, a design that can de-facto be used even if the barrel has to be custom-made by a third party without any suspicions)?

And, very importantly, how much bigger should the inner diameter of the barrel be than the ammo (so to fit hmmm... a luger 9mm, take 9.1mm or somthing?)

[amachinist]

A quick formula for determining the outer diameter requirements:
Do=Diameter outer
Di= Diameter of bore
P= Pressure (ie propellant pressure)
F= Safety factor (Recommend minimum of 2)
Y= Yield strength

Do=Di*(1+PF/Y)^0.5

Suitable materials (4140 and variants)
Din 1.7223 41CrMo4 Din 1.7225
BS708 M 40 42CrMo4
BS 3111-5/1 4140
SCM 440 BS708A42
42CD4TS 708M40
2244 SCM440(H)
SND7
42CD4
42CrMo4
2244

Just remember to utilize the diameter of the case for Do at the breech end.

[bobo]

ok, so far for being a beginner in a firearmophobic country... .I finished my barrel and hammerpiece with central firing pin, and then concluded that my ammo is rimfire:rolleyes:

So... any suggestions from here on? Do I keep on going, and construct some centerfire .22 ammo or is it better to change the relative position of barrel and hammerpiece/pin and go for rimfire?

[tomu]

Well bobo shit happens I guess.

What is the easier way? Do just have just finished drilling and chambering the barrel but haven't it fixed to the gun frame so my guess is it would be easier to fix the relative position.

If you make alterations in the ammo, you have do do this also in the future, which is a question of how often you would like to fire the gun.

[bobo]

It is a screw thread chambering right now. This would work for centerfire .22, but they are an oddity so it seems. Rimfire make this design a lot more difficult because the position of the pin hole is not central and can be in any position. I do not see a practical way to initiate rimfire ammo using a spring with this thing. This means I need to refill the rimfire cases and turn them into .22 centerfire (nearly impossible to do this right, so it will be shabby ammo or worse) or abandon the .22 caliber.

[tomu]

bobo would you please explain what do you mean by "screw threat chambering"? And what is the problem with rimfire ammo?

Maybe do a little sketch (free hand) post it somewhere to be downloaded and describe your problem with the spring and the firing pin.

[bobo]

screw thread: M12 thread on the "barrel". M12 thread cut into the "block". Like a hollow bolt and nut with a small hole in it.

[edit: aw hell, that ascii drawing was absolutely garbled after submitting, removed it]

The bullet (not drawn) will be squeezed in between tightly if screwed on. A firing pin on a metal bar with a powerful spring behind it is triggered ball point style. This way, the contraption is single shot, will not be reloading quickly but it is an object of minimal size consisting of four parts. The bullet will absolutely not fire its case backwards.

This is thus an utterly primitive thing, nothing to be proud of even once it succeeds but it'll serve for a useful lesson in improvising firearms and testing ammo.

[tomu]

Ahh...

I thought at first you hd cut the chamber with a tap.

Anyway why don't you use an offset firing pin? Just a steel rod where the firing pin is excentrically fitted to it. Or if the steel rod is too small a kind of fork with two prongs fitted to the small steel rod.

[bobo]

Yes, I'll have to drill one excentrically. The device will be a little more awkward (even more awkward) but this seems like the best way to adapt to rimfire.

[tomu]

http://www.youtube.com/watch?v=9T9UDasLeiA

Maybe this video of a crude made .22 single shot tilting breech pistol is of interest to you.

[wolfy9005]

just a thought, but for the barrel you could import a short section of seamless hydraulic tubing. it would be listed as hydraulic tubing, and so shouldnt be illegal. maybe ring up a few companies and ask for aome "sample offcuts" of the required I.D, then go from there. even if you only got a 7-8" 5.5mm I.D tube, atleast its better then a bolt of unknown consistency. also, it would simplify manufacture. just ask and say you are making a science project for your son(or yourself if your young enough) which involves making a hydraulic cylinder. just a thought. most companies will supply you happily, as it usually just goes in the bin anyway.

[sbovisjb1]

It is suggested to go with stainless steel, as it has higher resistance to elements and when you fire, it doesn't bend and warp as much, that said its MUCH more difficult to drill, ream and rifle.

[Setharier]

Talking about barrel making in general.

I was hypothesizing using a thin steel pipe 1mm rim strength, rifled, to being rolled on with several dozen, even couple of hundred times with finest mesh glass fiber one can get. You heard correctly. They used this stuff in a shotgun barrel in the 70's, but people didn't trust it and it didn't sold althrough was referred being even many times stronger than it's steely counterpart.

I have been planning of attempting making out such a construction when I have more time and equipment to complete it. I found airsoft barrels being readily capable of discharging 22LR cartridge through plank without any breakage or expansion in the discharging end, but no one can speak of accuracy: the bullet can be dropped through due to the wrong caliber ratio - .22 being 5.7mm and AS barrel 6mm min.

One could purchase 9mm innerdim. pipe and roll 300 layers fine mesh glass fibre in resin bath. In the chamber end one would roll twice as much, and even, at least partially, use the 9mm shell or a model made of it forming the chamber.

I bet this is worth of testing.

[kaiserbill]

Certainly sounds like it warrants further investigation. De Marco's shoulder launcher utilized PVC pipe strengthened with layers of glass fibre as well, albeit this was a recoiless launcher and thus subject to far lower pressures. A shotgun would be much

Setharier, do you recall the make of the 1970's shotgun you mention that utilized the external glass fibre strengthener?

[Setharier]

I don't remember just now on what decade that shotgun was actually manufactured but it had glass fibre barrel and said it withstanded several times the pressure of what similar steel barrel would have done.

About the barrels and material once again. There has been discussion of less powerful, mostly .22cal barrels. How about making 308Win machine gun barrel? The material choice seems absolutely more important on this. The cartridge produces 62,000 psi (430 MPa) or nearly 4300 bars of pressure.

"Rifle barrels are usually made from steel alloys called ordinance steel, nickel steel, chrome-molybdenum steel, or stainless steel, depending upon the requirements of the cartridge for which they are chambered."

I always tought stainless steel is very soft metal, but also heard that several rifle barrels are actually made out of it. Purchasing an 1" rod two feet long of stainless and then lathing it does not sound impossible nor too expensive in any mean.

[tomu]

...snip
I always tought stainless steel is very soft metal, but also heard that several rifle barrels are actually made out of it. snip...

A barrel should be tough and soft, usually well below 30° on the HRC scale to withstand the high dynamic stresses. A 42CrMo4 steel is quite suitable for a highpower barrel. Also most stainless steels will be ok.

[Setharier]

How comes the rifling? I quickly hypothethized using two pillars or other solid mass elements, car jacks and a hardened-steel rifling rod. The jacks easily push several tons and enable the rifling device to be pushed through the barrel.

Using the deactivated barrel unit would be laziest and easiest, but potentially dangerous way since the chamber has been drilled and tap pushed through it, severely weakening it. Anyway it could be drilled/slammed away and reinforce-mass-welded and I bet it would withstand about enough to make the gun act repeatingly.

[tomu]

How comes the rifling? ...snip

Using the deactivated barrel unit would be laziest and easiest,...snip

Your best choice is cut rifling somewhere on this forum is a threat about a video of Guy Lautards rifling machine. Making a rifling button for button rifling will be impossible without a toolmakers knowledge/skill and workshop.

There are some deactivated barrels on the market where only the chamber is welded shut and some short distance forward the chamber are some holes drilled through. If cut off the remainder of the barrel can be rechambered.

[Kaydon]

http://www.lindsaybks.com/bks6/rifle/index.html

I have not been able to find a copy floating about the web. It'd be a good find if someone did.

http://findarticles.com/p/articles/mi_m0BQY/is_12_47/ai_79586229

http://www.riflebarrels.com/articles/barrel_making/making_rifle_barrel.htm

Material info

http://ammtiac.alionscience.com/pdf/AMPQ8_4ART08.pdf

http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0774828