why are barrels octagonal?

[jrdavis]

But when barrels were created by hand-forging in the period, they were shaped around a round mandrel from a flat bar of iron that was forge-welded to create a tube. This yields a round barrel initially...

Modern barrels that are bored could conceivably be any shape.

that's true, but I believe they were forge welded in a swage block or gun anvil as noted in the book "Guns and Gunmaking tools of Southern Appalachia"

 

[jrdavis]

that's true, but I believe they were forge welded in a swage block or gun anvil as noted in the book "Guns and Gunmaking tools of Southern Appalachia"

a lot of it depends on what part of the swage block was used to i.e. round or 1/2 octagon. to me a wide flat piece of iron welded with one seam would make a round barrel some what easy to make . I think the barrel that were welded around the mandrel and edge welded were trued up in the half octagon swage block

 

[Archer 756]

How many of you have ever made a forged barrel !

 

[Carbon 6]

Many old barrels were not finished or filed on the bottom. A lot of builders apparently did not do any more than necessary .

That in of itself tells us much.

 

[Rifleman1776]

Who cares about the outside.

The claim in the American Rifleman magazine was that Gussler says the octagonal shape is an exterior representation that the bore is rifled. That struck me as quite possibly being an unverified myth for the sake of impressing the tourists. Personally, I am far less expert than many on this forum. But, I have been at this game for a half century and have visited more than just a few gun museums. Viewing the long guns in those museums would have illustrated this notion. I have never seen, or heard, it from any other source.

 

[Carbon 6]

Gussler says the octagonal shape is an exterior representation that the bore is rifled. .

This is true if we realize that it is a personal observation and not meant to be a rule or industry standard.

For the most part it still holds true today as an observation. If I see a gun with an octagon barrel, I am going to assume it's rifled.

 

[Sun City]

Then how does one explain the octagon to round barrels on tradeguns (smoothbore) and the Harper's Ferry (Rifle). This sounds like a statement made by an uninformed person who is pulling misinformation from a place where the sun doesn't shine...

"who is pulling misinformation from a place where the sun doesn't shine..."

Grin Grin!!

 

[Black Hand]

How many of you have ever made a forged barrel !

I fail to see how this is important. How barrels were made is well-known.

 

[Gene L]

In the earlier video of Williamsburg Gunsmithing, only the part of the barrel that showed was octagonal, the bottom was roughly round. I would think a perfectly round barrel would be more difficult to file than one with flats.

 

[19 16 6]

I fail to see how this is important. How barrels were made is well-known.

What Archer wrote is pertinent as is; Who here has done any blacksmithing school ?
Where they teach, draw square then hammer to octagon & on down till round & the reasons for doing so.
And all this because still some think that because the mandrill is round & the scelp flat that the hammering will also be round.

The drawing out of the metal is faster & therefore more energy efficient in arm movement & forge fuel. The taper is more controllable as is the straightness of the work piece.
To hammer round all the way is a botch & very difficult to do. Try it.

As stated by another poster earlier, even the big hammer forging barrel machines do it this way.

This stuff appears to not be understood or well known.
If a person has the practical experience then they know.
O.

 

[Black Hand]

What Archer wrote is pertinent as is; Who here has done any blacksmithing school ?
Where they teach, draw square then hammer to octagon & on down till round & the reasons for doing so.
And all this because still some think that because the mandrill is round & the scelp flat that the hammering will also be round.

Blacksmithing is no longer a secret art and the techniques used are well-known. The square to octagon to etc. is a great way to turn a piece of bar stock into a round profile, but isn't the way a forge-welded barrel is made.

Forge-welding a barrel:
The purpose of the mandrel is to serve as a backer to the hammer blows and keeps the tube from collapsing. If a piece of flat stock is hammered into a swage block to make it U-shaped, the edges overlapped and forge-welded with the mandrel inserted, the end product is roughly cylindrical. After straightening as much as possible, the bore is then reamed so it is the same diameter from end-to-end. The octagonal shape must be intentionally created afterwards, serving to center the bore on the barrel profile which makes mounting sights and sighting-in easier (an off-center bore can cause problems). The barrel is likely straightened a few more times during the process.
http://flintriflesmith.com/ToolsandTechniques/barrel_making.htm
https://www.bing.com/videos/search?...366DA2D5C602597530B0366DA2D5C602&&FORM=VDRVRV
https://www.bing.com/videos/search?...C3C928830645EA5EE46FC3C928830645&&FORM=VDRVRV
https://www.forgemag.com/articles/84439-gunmaking-forging-the-barrel
http://toadhallrifleshop.com/barrel-forging/

 

[jrdavis]

Blacksmithing is no longer a secret art and the techniques used are well-known. The square to octagon to etc. is a great way to turn a piece of bar stock into a round profile, but isn't the way a forge-welded barrel is made.

Forge-welding a barrel:
The purpose of the mandrel is to serve as a backer to the hammer blows and keeps the tube from collapsing. If a piece of flat stock is hammered into a swage block to make it U-shaped, the edges overlapped and forge-welded with the mandrel inserted, the end product is roughly cylindrical. After straightening as much as possible, the bore is then reamed so it is the same diameter from end-to-end. The octagonal shape must be intentionally created afterwards, serving to center the bore on the barrel profile which makes mounting sights and sighting-in easier (an off-center bore can cause problems). The barrel is likely straightened a few more times during the process.
...that wasn't the only way it was done they also forge welded by wrapping the iron around the mandrel and welding the edge to edge using like scrap iron like old horse shoes. to make a barrel of flat iron it would need to a little over 3 wide to make a one inch single seam Barrel....

 

[jrdavis]

 

[Black Hand]

That technique is probably what was used with the spiral-welded Damascus shotgun barrels. You can't leave the mandrel in the center when heating for a forge weld. It must be colder or it will weld to the barrel material.

If you notice, the core in the image above is hollow, so I'm not certain how well that would work if hammering for a weld. Hammer blows enough to weld would likely collapse the hollow tube at the core.

 

[nhmoose]

Octagons are lighter than a round barrel of the same size. Also easier to make smaller with hand tools than round. Try making a round barrel lighter by hand tools meaning files etc.

 

[jrdavis]

I have read that the large shops made round barrels because the had access to a lathe to true them up where the backwoods shops made octagon because the could use a file to true the up.

 

[jrdavis]

That technique is probably what was used with the spiral-welded Damascus shotgun barrels. You can't leave the mandrel in the center when heating for a forge weld. It must be colder or it will weld to the barrel material.

If you notice, the core in the image above is hollow, so I'm not certain how well that would work if hammering for a weld. Hammer blows enough to weld would likely collapse the hollow tube at the core.

they are not hammering on the tube but on the iron wrapped around the tube. and yes this is a shotgun barrel but rifle barrels were made this way also

 

[hanshi]

While my knowledge on such subjects is miniscule, I do now have the definitive answer for this question. Please understand that my wife is as far removed from BP guns as am I from birthing babies, or even moreso. I came to her, hat in hand, with this question; why are/were rifle barrels built otagonal? Ready for it?? This is THE true answer from the lady's very lips: "JUST BECAUSE"! There you have it, dear hearts; all in one humble post.

 

[Black Hand]

they are not hammering on the tube but on the iron wrapped around the tube. and yes this is a shotgun barrel but rifle barrels were made this way also

For the steel to weld, it must be heated to the proper heat. This will also heat the tube in your drawing and hammering on the iron exterior will also affect the tube and collapse the tube. The tube at the core doesn't magically stay cold and stiff. You can't have it both ways...

 

[nhmoose]

Barrels were forged around a solid core that was round, inches at a time so the core could be removed. There were blocks made that also allowed them to be forged into the OCT shape while doing so.

THAT is documented fact look it up in barrel making.

Then the bore was reamed. After reaming it was rifled with a cutter groove at a time.