4130/4140 Chromoly pipe for a muzzleloader barrel?

[Wudsruner]

Does anyone with more knowledge of steel and pressures know if a 4130 or 4140 Chromoly pipe can be used for a gun barrel? I am steering clear of black iron pipe after the advice I received earlier on here, but I have heard many people use Chromoly pipe as it is the same steel used in manufactured barrels sometimes. I know there are a lot of stresses in Chromoly pipe, but can anyone tell me if it's ok to use? I am planning to build a BP percussion shotgun and I would keep the loads right around 20-30 grains. Nothing more. Thank you all

 

[Rudyard]

Well I have no idea what the virtues of these fancy steels are as barrels but with such huge charges as 20 to 30 grains I would think you could use impurity ridden' sham damn' or' two penny Wendsbury scelp' with confidence . .
.Rudyard

 

[nhmoose]

GM makes barrels from both but they drill solid pieces not pipe.

 

[Treestalker]

4140 Chrome molybdenum steel is an alloy with a lot of good properties. The 'Moly' enables the steel to resist pitting corrosion, and the manganese helps steel to take a temper completely through the steel easily. Chromium adds strength to the steel, helps it resist rust, and also helps it take a polish better. 4140 is some really good stuff, high tensile strength, probably can take a lot of pressure, but I don't know how much. Pipe made from it would be guess. If it is seamless I would guess very good, but I'm not a metallurgist.

 

[JCKelly]

Pipe, regardless of what alloy, is NOT a good choice for a gun barrel. Problem is, or can be, that seamless pipe can have a crack along the bore. Right whwre yo cannot see it. Unless something goes wrong. I have seen this myself, both in common 1018 steel and in 25% chromium 20% nickel alloy meat for use at red heat.
Yes, I am a metallurgist. I have also done failure analyses on several muzzle loading rifles that have burst.

 

[Zonie]

I think that all of the pipe and most of the "seamless tubing" that is easily bought on the market is made by rolling and welding the pipe.
That basically makes a weak area right down one side of the tube or pipe where the weld joint is located.

There is a true "seamless" tubing made for special applications but it is very, very expensive and rarely found outside the companies that paid the high price to have it made.

This is why most of the companies that make gun barrels machine their barrels from solid bar stock. Drilling the long hole for the bore with a gun drill machine is less expensive than having true seamless tubing made.

 

[Sam squanch]

The price of a true manufactured gun barrel will be WAY cheaper than the emergency room bill......

 

[JCKelly]

And the costs of doing without fingers and/or eyes. These things do blow up, you know. Now & again something goes wrong. Good ol' "seamless" tube sometimes has a crack hidden along the bore, where the manufacturer cannot see it. I personally have encountered this on some 1018 seamless tube made in Michigan, which a friend was turning into a flint pistol barrel for me. Also have seen a serious bore crack in 25% chromium 20% nickel high temperature alloy pipe. Yes, I am a metallurgist. Have done failure analyses on a number of blown up muzzle loader barrels. Unpleasant to know the aftermath.

 

[billraby]

Don't use pipe for a gunbarrel. If you want to make a barrel, start with a solid piece of steel and bore it out. Yes, you will need some fancy tools that cost a lot of money. That is why not many people do it.

 

[Crow-Feather]

Have you ever figured how a pipe bomb works. Black powder in the middle plugged at both ends.

 

[hawkeye2]

" start with a solid piece of steel and bore it out.

And I'd like to add fro, a known and accepted alloy for gun barrels. Not just a piece of cold rolled steel or something from behind the barn or a scrap yard that looks like it would make an easy and nice gun barrel. Wudsrunner, this goes back to the previous post you started, still not a good idea. Chromoly has a place in the frame and roll cage of a race car and it's fantastic there but just not for a gun barrel.

 

[SDSmlf]

If you really want to ‘make a barrel’....

 

[Billy Boy]

Does anyone with more knowledge of steel and pressures know if a 4130 or 4140 Chromoly pipe can be used for a gun barrel? I am steering clear of black iron pipe after the advice I received earlier on here, but I have heard many people use Chromoly pipe as it is the same steel used in manufactured barrels sometimes. I know there are a lot of stresses in Chromoly pipe, but can anyone tell me if it's ok to use? I am planning to build a BP percussion shotgun and I would keep the loads right around 20-30 grains. Nothing more. Thank you all

You don’t need 4140 or it's’ ilk for a black powder firearm. Milder steels will serve very well and are no doubt stronger and more uniform than anything made in the 18th and 19th centuries. Also, higher chromium bearing steels will be much harder to finish with traditional methods.

 

[rickpa]

After all the good reasons given for not using tubing, consider this. You might only use 20-30 grains of powder. What about the next owner? Do you want that on your conscience?

 

[Wudsruner]

" start with a solid piece of steel and bore it out.

And I'd like to add fro, a known and accepted alloy for gun barrels. Not just a piece of cold rolled steel or something from behind the barn or a scrap yard that looks like it would make an easy and nice gun barrel. Wudsrunner, this goes back to the previous post you started, still not a good idea. Chromoly has a place in the frame and roll cage of a race car and it's fantastic there but just not for a gun barrel.

Thank you for all of your advice Hawkeye. I am 16 and I have a long life ahead of me that I don't want to risk over making a handheld pipe bomb. I have purchased a 12 gauge barrel, a tap and a breech plug and Im going to make a safe barrel soon. I value my life and appendages more than saving $50.

 

[SDSmlf]

I have purchased a 12 gauge barrel, a tap and a breech plu

Just a FYI, you will also need a bottoming tap to complete that thread in the barrel to properly seat your breech plug.

 

[ohio ramrod]

I myself would never use any kind of "pipe" for a gun barrel. The first gun I made , I used a special seamless steel tubing made specifically for aircraft hydraulics, since I worked for a small job shop that did subcontract work for Goodyear areospace. I had access to materials that most people would not have. That barrel worked quite well for a ten gauge shotgun. Most so called seamless tubing is made by stretching and rolling welded tubing to "cover" the seam. Some seamless tubing is truely seamless made by forcing a mandrel through a hot solid blank. But that is expensive and only available in short lengths compared to rolled pieces which are available in longer lengths.

 

[Powderandball]

For a muzzle loader it would give the shooter the ability to make heavier loads than you design for, so it’s not a bad idea to use a larger than normal safety factor if perhaps someone else where to load it. Even 30 grains of powder is a very light load for a shotgun, but for black powder the weight of the projectile is more important than the amount of powder. Are you going to shoot slugs with it or only shot?

 

[Powderandball]

" start with a solid piece of steel and bore it out.

And I'd like to add fro, a known and accepted alloy for gun barrels. Not just a piece of cold rolled steel or something from behind the barn or a scrap yard that looks like it would make an easy and nice gun barrel. Wudsrunner, this goes back to the previous post you started, still not a good idea. Chromoly has a place in the frame and roll cage of a race car and it's fantastic there but just not for a gun barrel.

Yes, I am a metallurgist. I have also done failure analyses on several muzzle loading rifles that have burst.

What’s the optimal steel for a gun barrel? Which mechanical properties should it have regarding Yield strength, tensile strength etc.? What should one be looking for when picking a gun barrel steel (to be drilled out of solid barstock)?

4140 is a common gun barrel steel, and it’s a kind of chromoly steel. There’s different types of chromoly steels with different properties, and different heat treated conditions create different mechanical properties.

Here’s a chart of high strength chromoly steels: 34CrNiMo6 Which of them are suitable for a gun barrel? If we was to manufacture a gun barrel to contain high pressure and still have a thin wall thickness, like the revolver cylinder of a .454 casull, which steel is the best choice?

 

[Zonie]

We can talk about the types of steel suitable for a rifle barrel but we can't talk about cartridge guns on the forum.

As for the steel that is suitable for a regular traditional muzzleloading rifle or pistol barrel, low carbon 1018 or 1020 will work. There is no need for high strength alloy steel barrels or cylinders.

Generally speaking, black powder produces its gas pressure rather slowly when compared with modern smokeless powder and although black powder is classified as an explosive, it is a low power explosive.
That is not to say that black powder can't create high pressures. Although the typical pressures in a muzzleloading shotgun run around 2,000-4,000 psi and a muzzleloading rifle shooting patched balls run around 6,000-10,000 psi, a black powder load under a heavy lead slug can be over 25,000 psi. That's getting into the same pressure areas that smokeless powder can produce. The difference as I mentioned, is that black powder does not produce the sudden shock of pressure that smokeless powder produces when it ignites.
That is why a relatively weak low carbon steel will work in a muzzleloading gun. It is also why muzzleloading guns will often blow up if a smokeless powder is used in them.