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From: "Jim Wilkins" <muratlanne@gmail.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Barrel making using draw-over-mandrel?
Date: Sun, 18 May 2025 17:55:27 -0400
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"Bob La Londe"  wrote in message news:100d5jv$13flp$1@dont-email.me...

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.
[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."
-- 
Bob La Londe
------------------------------------------
When I found myself becoming a custom scientific instrument builder I 
collected available how-to books from other technical craft fields including 
gunsmithing, which proved to be mostly a dead end for what I needed to make. 
I did use the smoking and scraping method to fit a heatsink into close 
contact. I saw that self-protective guild mentality you mention, perhaps 
more for sporting arms than military ones where parts are contracted out. 
Working for The Mitre Corporation may have given me an edge since everyone 
knew they were special and important but not what they actually did. (X-File 
stuff?)

Auto companies and Segway were particularly tight with information, at GM 
the departments shared as little as possible even among themselves. Segway 
hid new developments behind disinformation.

My car is an example of the consequences of a leak. Land Rover was 
struggling financially in the 90's and tried a joint venture with Honda 
among others. They innocently sent Honda the body drawings of the 
developmental Freelander and then were upset to see Honda combine an Acura 
engine and the AWD drive train of their ugly Civic Wagon with the relatively 
acceptable Freelander body to introduce the CRV, before the Freelander was 
ready. Honda's target was the RAV4, not LR. I still prefer its practical 
Land Rover interior to the more stylish later models. It's the first 
generation with the folding picnic table for the cargo area floor, which I 
covered with plywood to protect it from heavy machinery like the nearly 100 
Lb carbide grinder. The Honda mechanicals were trouble-free for 20 years, 
then the rubber and plastic (radiator, harmonic balancer, engine mounts etc) 
began breaking down.
jsw