The Big Guys... and Gals

Really big ones.
See here:
"List of the largest cannons by caliber"
Notice, you're up to number eleven before you even hit the 20th century with what we consider the serious biggies; like those of the Yamoto at 18.1 inches.
The ten listed first are seriously old-school.
Just as a matter of house-keeping we'll dispense with The Tsar Cannon, the largest, with a bore of thirty-five inches and change, because it was only fired - if at all - as a ceremonial gesture.
It's the biggest but it exists as a novelty, not a tactical weapon.
The first of the runners-up: Plumhart von Steyr, of the Hapsburg Empire.
Okay, obviously Plumhart is more of a mortar than a cannon but we'll overlook that in light of the fact that it, like those following, is a bombard.
As the name implies, these monsters were used to bombard... fortress walls.
Once the range was found, simply loading and firing the same charge (30+# of black powder - for this gun) and the same 1500# projo (chiseled out of rock) again and again 'till, over time and six to eight rounds a day, would bring about the collapse of the wall and the fortress was then breached.
The etiquette of the day (14th to 15th century) held that, when the walls were breached, the defenders would give up and the siege would be lifted... theoretically.
Anyway, the above pictured, ugly bad boy sported a bore of 32 1/4"
Next up - at least of those extant is Dulle Griet coming in at just under twenty-six inches.
Her name comes from a Flemish folk tale "Mad Meg" (See her here: courtesy of Pieter Bruegel the elder)
On this gun I'm going to talk construction.
Old Plumhart above is the largest, wrought-iron bombard in the world (the Tsar Gun is cast bronze.) but this one actually has stats regarding what it was made of.
First, let me comment on the color: In the story of Mons Meg (patience) it was written that the British painted all of their royal cannon with red lead as a rust preventative.
That jarring, international-orange slathered on the above is the stuff. The bane of boatswain's mates since the days of wooden ships and iron men.
Back to bidness; You know why they're called gun barrels? 'Cause they used to be built like barrels - staves and hoops.
Old Meg consists of 32 sticks of wrought iron, 16 feet long, precisely beveled (Just like barrel staves) and held together with 61, wrought-iron rings, each of which was forged individually, welded into a circular shape just shy of the required diameter, heated white-hot and driven down over the tube.
The video at the end illustrates to concept on a smaller gun with a rolled barrel.

The structure can be seen clearly in the above photo. This is a bombard with no pedigree listed with the photo but we'll assume that the crew of men who lovingly tended her must have called her something.
The first thing to notice is the staves. Beveled - but not forge-welded. Imagine forge-welding a sixteen foot strip of iron to thirty-one others; previously welded. It wouldn't have happened.
Each of the rings were forged separately and driven on and that is where the strength of the gun lays.

Wrought iron is very cool stuff in that it has a grain - like wood.
Due to the way it's made (Was made. Now it's only available as old scrap or as a boutique product) it has a linear crystalline structure, further enhanced by microscopic slag inclusions (Also linear - between the crystals).
The end result: a very tough metal (non-brittle) with excellent tensile strength - in line with the grain - just like wood.
The staves of the gun were structurally functioning mostly to keep the barrel rigid and to hold the shape while the rings were driven on.
The rings, being forged and welded at the ends, retained all the tensile strength of the iron because simply punching the appropriate hole in a disc of of wrought iron would leave cross-grain - poor tensile strength.
Of course, none of this means anything with modern steel. It has no built-in direction even though some producers of overpriced, under-qualitied knives (Cold Steel) seem to think it does.
Which brings us to the crux of the biscuit and the reason why this is such a logical means of construction.
Not to say that modern cannon should be built this way. it's just that the more up-town technique, casting seems so much more sophisticated.
They both worked - many times over. The afore-mentioned Tsar cannon was cast from bronze.
The problem with a cast cannon is that the pressure is contained by just one unit. A monolithic, massive unit to be sure but one whose interior is invisible. A giant slag inclusion in a cast cannon could ruin every body's day if it blew out.

But, there's a lot to be said for a system where stress is parceled out in bits and pieces.
Case in point: number seven on the list with a bore of only twenty inches, "Mons Meg" (Another Meg!), so called because she was built in the Belgian city of Mons.
Mons, you may recall is where the BEF first butted heads with Kaiser Willie's lads during that golden August of 1914. The meeting which precipitated a most spectacular and orderly - although ignominious - retreat.
A seventy-thousand man contingent of the world's most professional army going against the second largest army on earth... while said 2nd largest was simultaneously fighting the 3rd largest to the south and bracing for the onslaught of the largest army off to the east. Good times...
Anyway, Mons Meg was put together in 1449 and, stories differ as to how, ended up in the possession of the Scots.
They used her to hurl big rocks at the English for a time and she served admirably.
However, she eventually experienced a blow-out.
"The gun was fired in 1680 to celebrate the arrival of James Duke of Albany and York, later King James II of England and VII of Scotland"
To be fair; the old girl was on her 240th birthday so it would make sense to figure she'd be a bit fragile.
The rumor is: the shot was loaded by an English cannoneer who may have overloaded it due out of jealousy since Mother England had no such boss ordnance.
The ball was found (According to the story) two klicks away.

Here's the damage.
Hardly a catastrophic failure. It broke one ring - didn't even bend (Looks like) the staves.
Now, the explosion of the "Peacemaker" aboard the USS Princeton in 1844 was a catastrophic failure and a good illustration of the linear vs transverse strength of wrought iron,
If Mons Meg's mishap had occurred in the heat of the moment instead of just at a ceremony, this old bitch could have still have thrown rounds down range.
Okay, I've illustrated the principle proving that a lot of little, weak parts can be better than just one big... part.

Here's a down and dirty demo of the making of a wrought iron cannon. It's a little one so the tube is a rolled sheet but the reinforcing rings are identical.
The comments are hilarious. "Why didn't they just cast it in one piece?" Like that's easier.
On the subject of of cast guns, we'll touch on "The Dardanelles Gun" to finish up.
The Dardanelles are, of course, the choke point between the Sea of Marma and the Black Sea. A bit to the west is the Hellespont, home of the disastrous Gallipoli campaign.
As long as there have been hotly contested chunks of real estate in the world, this has been one of them.

Anyway, the Dardanelles gun was cast - inspired by those cast by a Hungarian named Urban whose bombards knocked down the walls on Constantinople in 1453 thus making it Istanbul - in 1464.
The shift from Constaninople (formerly Byzantium) to Istanbul is lucidly explained in this video by They Might Be Giants (They did the theme song for "Malcom in the Middle" - and they might actually be giants.)
So Constantine's city fell and those Godless Muslims covered up all the mosiacs in the Hagia Sophia but... to the victors go the cool buildings.

About ten years later, this unit was commissioned.
24 7/8" bore, 18 tons (both chunks) and wicked bad.
It was, for a time set up to overlook the straits, the better to shell ships that may not be welcome in the Black Sea.
Fast forward from 1464 to 1807.
The Dardanelles Operation wherein the British thought to show those rag-heads who was boss and got their ass soundly whipped by this old antique as well as some of her sisters.
Twenty-eight Brit sailors dead and a solid Ottoman victory.
What I love about this old thing is this: One of the innovations brought to the table by the gun's designer/maker, Munir Ali, was the two piece construction seen above.

And that is where I fall in love with her.
Check out the picture. The two pieces (Probably 9 tons each as the smaller is the chamber/breech and contains a larger quantity of solid metal.) just screw together!
Now, I'm not throwing rocks at Munir Ali and his innovation at all. It's just that... I can't get my head wrapped around this concept where two parts of a whole - are threaded together - weighing nine tons apiece.
Just pick 'em up and screw 'em together. Righty - tighty, lefty - loosey.

Yeah, yeah. That's what those handy rims are for - levers and such.
Or a twenty-foot pipe wrench and teflon tape on a roll like paper towels.
Okay, gettin' silly.
Me, out.