Just idle curiosity.

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

From a position of total naivete, it seems like an obvious way
to get a very straight tube with a non-circular bore. AFAIK,
nobody does it that way.

What's the rub?

Thanks for reading,

bob prohaska

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Jim Wilkins <muratlanne@gmail.com> wrote:

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.

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

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On 5/18/2025 10:05 AM, Jim Wilkins wrote:

BP wrote in message news:100d0r8$12ddo$1@dont-email.me...

Jim Wilkins <muratlanne@gmail.com> wrote:

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.

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.

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."



--
Bob La Londe
CNC Molds N Stuff

--
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On 5/18/2025 10:32 AM, Bob La Londe wrote:

On 5/18/2025 10:05 AM, Jim Wilkins wrote:

BP wrote in message news:100d0r8$12ddo$1@dont-email.me...

Jim Wilkins <muratlanne@gmail.com> wrote:

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.

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.

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.




--
Bob La Londe
CNC Molds N Stuff

--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

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