Barrel making using draw-over-mandrel?

Does anybody make rifled gun barrels by drawing over a mandrel?

---------------------------- Button rifling is a mandrel drawing process that presses in the grooves.

I'm not really into gunsmithing but I've studied it from the angle of its importance in the Industrial Revolution, see

Around the time of the US Civil War military barrels were rolled out from short thick blanks over a mandrel, then drilled to size, rifled and straightened by expert hands. For military muskets and then rifles the demand for accuracy wasn't as great as the need for quantity, after the first volley troops couldn't aim through the smoke.

It's still done and makes very good barrels.

"A cold hammer forged barrel starts life, so to speak, as a short and fat blank with a polished hole running through the center. A hardened mandrel of proper width (caliber) and rifling pattern—again reversed/inverted—is placed into the smooth bore. The pair go into a forging machine that compresses the steel against the mandrel, hammering it into final shape."

Relatively few of the many technical improvements that have been tried succeeded, hindered by black powder fouling and the low and variable quality of wrought iron and steel before the 1880's.

When smokeless powder and modern steel became available in the late 1880's firearms very soon assumed forms that have survived until today, such as the Mauser bolt action and Winchester and Marlin lever actions of the 1890's. Military tactics and uniform colors changed to match.

"I feel the 6.5x55 Swedish suffers from the same fate as the 7x57 and 8x57 Mauser, in that much of the factory ammunition isn’t loaded to its full potential. When it is loaded properly—as in the Hornady Superformance line—it is fully the equal of the much more modern 6.5 Creedmoor."

Skirmishers with accurate rifles used modern tactics of cover and concealment but they were too vulnerable to cavalry for that to be standard practice, in the open a dense wall of bayonets or pikes was the only relatively sure defense against a charge. Waterloo is a good example of infantry vs cavalry, and then only after both sides were running out of alternatives.

In WW1 it became painfully obvious that horse cavalry was obsolete, just as armored cars and then tanks became available. Germany depended heavily on horses during WW2, only the US was fully motorized, with men who already could drive and maintain vehicles. "The United States had 1:5 ratio of cars to people, while the ratio in Germany was 1:89..."

For an Army license to drive in Germany I needed to pass only a regulations and sign reading test, they assumed everyone could drive. There were around

120 signs to learn, fortunately I knew the words.

The rock drill rod I'm making a part from is a thick walled tube with the hole visibly off center. My next step is cutting the M24 x 1.5 internal thread, after practicing on aluminum.

At least superficially the DOM process could combine drilling, rifling and straightening steps into one, or at worst two, using nearly identical machinery. What am I missing? Is the problem a too-small final ID?

It does occur to me that the pull strength of the internal mandrel grows as the square of the diameter, while the pull force likely grows linearly with the circumference. I suppose that would set a lower bore limit....

Thanks for writing,

bob prohaska

At least superficially the DOM process could combine drilling, rifling and straightening steps into one, or at worst two, using nearly identical machinery. What am I missing? Is the problem a too-small final ID?

It does occur to me that the pull strength of the internal mandrel grows as the square of the diameter, while the pull force likely grows linearly with the circumference. I suppose that would set a lower bore limit....

Thanks for writing,

bob prohaska

------------------------------------- What you are missing may be proprietary trade secrets concerning the relative strengths and weaknesses of hammer forging, button rifling and drawing over a mandrel, all of which are similar. I suspect the fittest survived.

The answer may depend on plastic deformation and work-hardening of a thick walled pressure vessel, which is one with varying stress and strain distribution across the wall thickness. Before tech permitted big gun barrels to be forged in one piece they were built up from concentric cylinders successively heated to expand them and shrunk together, preloading the inner layers with compressive force. Expanding the barrel over a mandrel might have the opposite effect, or see below.

"Theoretical maximum performance would be achieved if the inner cylinder forming the rifled bore were compressed to its elastic limit by surrounding elements while at rest before firing, and expanded to its elastic limit by internal gas pressure during firing."

This is more or less what you suggest:

"In modern practice, a slightly oversized die is pushed slowly through the barrel by a hydraulically driven ram." I didn't learn nearly enough in one semester of Materials Science to understand the subtleties of plastic deformation beyond the yield point.

There is definitely a certain amount of derogatory push back against the un-anointed in the firearms industry. I have two books on gunsmithing. titles Basic and Advanced. Both authors spend the first chapter ranting about cleanliness and organization. In other chapters they get into painstaking detail about it taking away from the main topic as well. Then they talk about things like heat treating either in mysticism that can't be shared with somebody who had to buy a book, or in very advanced technical terms and advanced general material formulas intended to weed out and actively shun those who just want a reliable recipe. My college math ended with Finite Mathematics (supposedly Calc for finite sets of data primarily for programmers and data analysts). This left me struggling with most of it without asking my son who could easily teach calc and has tutored many other students.

The thing is a lot of things can be figured out in reverse. If you don't mind marking up some guns you can use tools as simple as a set of hardness files to get a ball park for the hardness of a part. Reliable recipes for hardening various alloys are as close as your cellphone. If you aren't wildcatting hot loads you can build a safe firearm by working backwards and ignoring the fat ugly old wannabe gun bunnies who worship at the alter of the anointed and deride any who dare to learn.

Okay, that was a bit harsh. There are some great guys in the industry, but most just don't respond when you ask modestly technical questions. They may know the answer you seek, but they just don't say anything. You can always get a bunch of people to tell you how stupid you are when you just say what you plan to do, but unlike other topics giving the wrong answer on the Internet doesn't usually illicit the right answer.

There are a couple guys on the gunsmith section on Home Shop Machinist that are helpful if they can be, but answers to hard questions sometimes end with, "Well you should build a gun for a low pressure cartridge instead."

There is a YouTube gunsmith that also shares pretty good stuff. Mark Novak. He does a lot of repair and restoration work. Generally he tells you what he's doing, how he's doing it, and sometimes why. Of course its not as fast as reading a tutorial, but I am thankful for what he shares anyway.

There is definitely a certain amount of derogatory push back against the un-anointed in the firearms industry. I have two books on gunsmithing. titles Basic and Advanced. Both authors spend the first chapter ranting about cleanliness and organization. In other chapters they get into painstaking detail about it taking away from the main topic as well. Then they talk about things like heat treating either in mysticism that can't be shared with somebody who had to buy a book, or in very advanced technical terms and advanced general material formulas intended to weed out and actively shun those who just want a reliable recipe. My college math ended with Finite Mathematics (supposedly Calc for finite sets of data primarily for programmers and data analysts). This left me struggling with most of it without asking my son who could easily teach calc and has tutored many other students.

The thing is a lot of things can be figured out in reverse. If you don't mind marking up some guns you can use tools as simple as a set of hardness files to get a ball park for the hardness of a part. Reliable recipes for hardening various alloys are as close as your cellphone. If you aren't wildcatting hot loads you can build a safe firearm by working backwards and ignoring the fat ugly old wannabe gun bunnies who worship at the alter of the anointed and deride any who dare to learn.

Okay, that was a bit harsh. There are some great guys in the industry, but most just don't respond when you ask modestly technical questions. They may know the answer you seek, but they just don't say anything. You can always get a bunch of people to tell you how stupid you are when you just say what you plan to do, but unlike other topics giving the wrong answer on the Internet doesn't usually illicit the right answer. [elicit?] There are a couple guys on the gunsmith section on Home Shop Machinist that are helpful if they can be, but answers to hard questions sometimes end with, "Well you should build a gun for a low pressure cartridge instead."