swamping a barrel

[dave gross]

Can anyone here explain to me how in the years between large files and cnc equipment barrels were profiled...I am aware of some of the equipment used but can't envision how it would have been set up.  Thanks for any info.

Dave Gross
Downeast in Maine

[chris laubach]

The taper and flare (swamped) is produced during the forging process. The barrel is made by forging a “skelp” into a tube. When laying out the skelp you create the taper and flare in the flat piece of iron. When this is forged welded around a mandrel the tube also becomes tapered and flared.

We get more in depth in this video;

https://www.artisanideas.com/product/102122/Forging-a-Flintlock-Rifle-Barrel-with-Jon-Laubach-and-Chris-Laubach-DVD.html

There where also grinding mills during the period but I would think you would still forge the profile in the barrel first.

CL

[Daryl]

I think that is likely correct - forged to shape, then ground smooth.

[Scota4570]

If I understand the question, how could this be accomplished with non CNC machine tools, say a 1940 level of tech?   

I never did it but I speculate that I would have used a horizontal milling machine.  The barrel would be held by the ends and the waste area jacked up.  You would want two sets of jacks to accommodate a cut flat and a virgin flat.  Multiple hold downs  would be needed to avoid chatter.  The milling cutter would then be run side to side over the created high spot.  When taken off the table the barrel goes back to the previous non bent condition with a waist. 

I am sure somebody here as first hand experience. 

[DGB]

Swamped barrels or many other shapes were created on milling machines with a "rise and fall" feature. The head with the cutter followed a template with the desired shape on it which caused the head to rise and fall as it followed the template.
This technology has been around since very early times , and is probably still in use in some areas of the world as well as here in less well equipped shops. The template could be hand made with a file if that's all you had.

Regards,
DGB

[Clowdis]

More than you think were done on shapers and mills by bending the barrel and planeing the flats.

[Tim Ault]

I’m not a machinist by any stretch but could a surface grinder be used in a similar way . Clamp down the ends and bow up the middle .  We have a rather large machine at my job they use for resurfacing our die beds .

[rich pierce]

A surface grinder won’t be efficient for removing tens of thousandths of an inch.

[JHeath]

If you have a vertical mill but no rise and fall cutter, you could make a long stepped series of cuts with an end mill around the "circumference " save a lot of the filing, and get consistent dimensions.

Clamp the barrel on the table against an end stop.  Set depth, run the table in and out to make a cut transverse across one flat of the barrel. Rotate the barrel and take another cut etc. Traverse the table, reset depth, repeat.

You'll then have a series of gentle steps to blend by draw filing. But a lot less filing and you won't be eyeballing so much.

The barrel will be resting on the intact flats at each end.   As you progress, the barrel will become unsupported across much of its length. You'll want to feed slow to minimize deflection and/or stuff shims under to support it.

No, I haven't done this before. I am literally sitting in an armchair playing gunsmith.

[Bob Roller]

Bill Large swamped them on a planer by capturing both ends between centers and the raising thecenter with a small but powerful screw jack.After all 8 flats were done he would then straighten the bore with a barrel jack which was a a special
tool that was used in shops where straight holes were needed.It used the power of a fine thread screw controlled by a hand wheel and the barrel was held by supporting it so it can be easily moved.
Bob Roller

[little joe]

Than you Bob Roller

[Birddog6]

I know of several people that have swamped a barrel by hand with hand files.

They only did one. 

[Scota4570]

You only need to deflect the barrel about 1/16" to make the waist.   

[Daryl]

I know of several people that have swamped a barrel by hand with hand files.

They only did one. 

I didn't swamp a barrel, but did convert a round barrel, into a 1/2 tapered octagonal 1/2 tapered round barrel using files. I did only one.

[JHeath]

You only need to deflect the barrel about 1/16" to make the waist.

The idea of deflecting a barrel freaks me out. But if it's only 1/550 of the span then I would expect it to spring back. Although the apex is far from center span.

[tecum-tha]

I am filing right now