Shotgun action vs double rifle action?

My 2c worth.

Shotguns are low pressure firearms so generally don't have as heavily built an action as a double rifle. While you can make rifle barrels that fit a shotgun's action the barrels would need to be spaced really far apart for the primers to line up with the firing pins because the cartridges are so much smaller.

There are many examples of O/U configuration double rifles from cheapies from Baikal all the way to high end stuff from the likes of Heym, Merkel, Purdey etc.

I think that S/S are more common because they can be lighter but that's a guess.

I once talked myself out of buying a 45/70 Baikal O/U that had started out as a 12G. The existing barrels had liners pressed in and it was laughably heavy. Seller told me it had been built for his dad as a bush pig hammer.

The history of the over/under shotgun is indeed fascinating! Let’s delve into it a bit further.

Origins and Purpose: The over/under shotgun, also known as the O/U, emerged in the 20th century as gunmakers sought to create something new and appealing. Prior to this, side-by-side shotguns were prevalent, especially in Great Britain. However, the O/U gained prominence when clay target shooting started gaining popularity. Gunmakers looked to game shooters to drive demand, leading to the development of the O/U1.
Challenges in Design: Creating an elegant over/under shotgun posed challenges, particularly in jointing the barrels to the action. Unlike side-by-side designs, which used barrel hooks and rear bearing surfaces, the O/U needed a different approach. James Woodward, a renowned London gunmaker, devised a solution involving draws, wedges, and reciprocating surfaces. This method resulted in an elegant appearance, seen not only in Woodward shotguns but also in more affordable options like Perazzi1.
John Browning’s Influence: John Browning, the prolific American gun designer, played a significant role in shaping the O/U. His approach prioritized strength and rugged reliability. Browning’s under-bolted superposed O/U featured a substantial barrel hook pivoting on a full-width cross-bolt. This design emphasized practicality and durability, appealing to a broader audience1.
Beretta’s Contribution: In the 1930s, John Browning’s success with the O/U inspired Italian gunmaking giant Beretta to enter the market. Beretta introduced the sidelock Sovrapposto (also known as the Beretta SO), further contributing to the O/U’s legacy1.
Historical Traces: While the O/U gained prominence in the 20th century, there are intriguing historical traces. For instance, Beretta produced an over-and-under wheellock musket in the late 1600s, suggesting that the concept of an O/U shotgun dates back at least 300 years2.
In summary, the O/U shotgun’s evolution involved innovation, aesthetics, and practicality, making it a beloved choice for both sporting and hunting enthusiasts. Whether you’re a clay shooter or a game hunter, the O/U continues to be a classic and versatile firearm

No offence -but - this appears to be a copy and paste ?
There is no link or attribution ... ?

Correct, Wiki. It however gives general info and saved me time in writing a whole spiel.

No offence -but - this appears to be a copy and paste ?
There is no link or attribution ... ?

********************************
I did not think there was any pretense for it to be seen as any other presentation.

So, the actions are then very different, Diesel/Petrol kinda different. I wondered about centering the firing pins and primers.
At one stage i was very gingerly looking into the prospect of getting some of those rifled shotgun barrels and making a rifled S/S to shoot slugs from a shotgun at shotgun pressures.
This was gonna be my beeeg "Daaadddaaaa!" moment, but I lost steam as old age and sensibility set in.