why are barrels octagonal?

[Coot]

My understanding is that octagonal barrels were easier to forge into shape and then to finish with fewer tools/equipment - finished by drawfiling by hand. Round barrels are shown in period illustrations being ground round on huge water powered grinding wheels in large commercial works which were beyond the means of many/most American riflesmiths. As a result of the equipment available, most early American made rifles would have hand filed octagonal barrels while most early round barrels would have been imported from large works in England. Once powered machine tools came in, any shape or taper could easily be made but a round, tapered barrel became dominant as it was both lighter and cheaper than any other shape. As mentioned in an earlier post or two, both rifles and smoothbores were/are found with octagon to round barrels which, due to the round part, I believe may largely be the products of commercial barrel makers rather than small shops - just as most locks were made by specialists rather than individual gunsmiths.

 

[Black Hand]

My understanding is that octagonal barrels were easier to forge into shape and then to finish with fewer tools/equipment - finished by drawfiling by hand. Round barrels are shown in period illustrations being ground round on huge water powered grinding wheels in large commercial works which were beyond the means of many/most American riflesmiths. As a result of the equipment available, most early American made rifles would have hand filed octagonal barrels while most early round barrels would have been imported from large works in England. Once powered machine tools came in, any shape or taper could easily be made but a round, tapered barrel became dominant as it was both lighter and cheaper than any other shape. As mentioned in an earlier post or two, both rifles and smoothbores were/are found with octagon to round barrels which, due to the round part, I believe may largely be the products of commercial barrel makers rather than small shops - just as most locks were made by specialists rather than individual gunsmiths.

Lest we forget, barrels and locks were also imported/purchased from manufacturers. Many other parts were made or could have been made on site by the gunstocker. I can't say how many built guns from the bottom-up (sorry - lock, stock & barrel)...

 

[Canute Rex]

What Coot said.

Speaking as a blacksmith, if I have a round rod, like a just-welded barrel, and I want to hammer it into a shape with flat sides, octagonal is the most straightforward. Hammer flats 90 degrees apart and then turn it 45 degrees and hammer more flats 90 degrees apart. Not quite round, but easier to hammer than hexagonal and not a lot of extra material. Much easier to hammer than a 10-sided or 12-sided form.

Also much easier to inlet into wood with vertical sides, a flat bottom, and only a 45 degree angle to deal with on the other two flats.

 

[Loyalist Dave]

OOOH I HAVE IT.....
OK so the 8 sides of the octagonal barrel represent the "Seven heavens" plus the realm of the Earth = 8...so it was thought that the rifle would shoot much straighter by "invoking the seven heavens and the Earth."

HEY if we're going to have some myth about the number of flats on a rifle barrel, let's do it right!

LD

 

[8 BORE]

Boy this is getting old.
Who cares about the outside.
Whats on the inside is what matters.
Maybe barrels made from pvc pipe.
Let you techno professors have a go at that. That should be more amusing than boring.

 

[Black Hand]

Boy this is getting old.
Who cares about the outside.
Whats on the inside is what matters.
Maybe barrels made from pvc pipe.
Let you techno professors have a go at that. That should be more amusing than boring.

If you don't care, stop posting. Those who wish to discuss should be free to do so...
Muzzleloaders are as much art as mechanics - the aesthetics are important too.

 

[M. De Land]

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.

Modern forged barrels are done by a rotary hammer that leaves the exterior round. It must be so for the mandrel to evenly impart the rifling sharply, into the barrel bore.
All modern barrels are milled into octagon then many are stress relieved afterwords.
All I have ever read is that originals were made octagon for styles sake. I've also seen a few six sided (hexigon) barrels.

 

[Black Hand]

Modern forged barrels are done by a rotary hammer that leaves the exterior round. It must be so for the mandrel to evenly impart the rifling sharply, into the barrel bore.

Interesting. I was under the impression the rifling was cut rather than embossed on the bore.

 

[Carbon 6]

Muzzleloaders are as much art as mechanics - the aesthetics are important too.

Worth repeating.

 

[19 16 6]

There is a formula for this.
If you read the posts saying that eight sides is the forging norm then to round goes 16 sides, 32 & on until it has the appearance of round. It is still many flats because it is all you can do on an anvil with a hammer.
So eight sides is quick in the forge saving fuel & time. Cheap
Then the file is flat for creating flats to finish the job flat without spending months on the filing. Easy & lazy.

After this easiest fastest cheapest way of doing things is done it becomes the normal thing to expect that your gun has an octagon barrel.
Then because the Joneses have one, ours needs to be the same. Stupid.

So the formula as I worked it out in the construction industry is, if you even have to ask the question why something was done that way then apply the formula.

Cheap & easy, stupid & lazy. You find the answer in that.
O.

 

[Carbon 6]

Here's how Pedersoli makes barrels.

 

[tenngun]

16th century saw some hexagonal and pentagonal shapes. And square was to be seen. No explanation in of itself makes sense.
You have to have a flat-to set a lock against. Easier to file? Then why leave military guns round? It’s not easier to inlet, and swamped or tapered ruins that explanation. It gives a flat on top and a flat on the side but weighs less then square?
Since so many civilian and trade guns were made with it, or with half octogon, in so many places, I just have to think style.

 

[TFoley]

A hexagonal barrel would be heavier than either a octagon or round barrel of the same caliber.

So why not ten-sided? Or even 12-sided? Serious question.

 

[Coot]

So why not ten-sided? Or even 12-sided? Serious question.

Canute Rex addressed this in his earlier post. Working in a simple shop without large production equipment (or many workers), an octagon is easier to forge on an anvil & finish with just a few hand files. When planning to produce thousands of barrels, such as muskets or for a large commercial market, then the investment in water powered equipment such as very large (well over a foot wide) grinding wheels, & hiring a number of semi-skilled workers, makes grinding the barrels round more efficient than draw filing flats.[/QUOTE]

 

[Artificer]

The common way to grind gun barrels round in the 18th century was for the semi-skilled grinders to lay on a elevated board over the grinding wheels.

I couldn't find an 18th century engraving of this being done for gun barrels, but here is an engraving of them doing it with somewhat smaller width wheels for sword blade grinding.
https://www.granger.com/wmpix/ind/s...rmill-from-LEncyclopedie-of-Denis-Diderot.jpg

Here is a 19th century engraving of gun barrel grinding on larger wheels.
http://media.gettyimages.com/photos...-a-gunbarrel-to-picture-id615321056?s=594x594

Gus

 

[Carbon 6]

So why not ten-sided? Or even 12-sided? Serious question.

Why not four sided ?

I think it was Gussler that said " the sound most often heard in an 18th century gun shop was that of filing."

 

[brayhaven]

I've often wondered why they were not hexagonal, since a hexagon shape is far easier to calculate than an octagon.

They needed flats on top, bottom and sides.

 

[brayhaven]

Why not four sided ?

I think it was Gussler that said " the sound most often heard in an 18th century gun shop was that of filing."

And the most often heard sound in a 21st century gun shop is “epoxeeee!”

 

[Carbon 6]

They needed flats on top, bottom and sides.

I like that answer, it fits my theory.
4 sides meets that requirement but is too heavy, so you file off the corners and get an octagon.
Anything with more sides than an octagon it to much work for any savings of wieght.

So then the question is how do we deal with weight of an octagon barrel ?
Answer; You swamp it.

 

[Pete G]

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