As Hawg pointed out , there is a difference between Steel and iron. BIG difference .
Silver steel was the initial stages of making steel . While it still wasn’t the steel we know today , it was much harder then iron
A forged barrel stock is rounded at least initially while being formed around the mandrel and during the hammer welding process by the use of forming / swage blocks .
While flats can also be initially formed during this same process , they still have to be draw filed to clean them up. Thus making any octagon derived from the forging process , nothing more then an initial starting point for the flats which must be trued and brought down to final shap and thickness .
Iron barrels depending on who was making them and the type being made, were either a forged sculpt “ think welled seam” or wrapped around the mandrel like they did Damascus which produces a lot longer weld.
Mixing of different irons and iron contents produced stub, pattern and later the highly patterned Damascus type barrels. I would be greatly surprised to read that colt used any of those processes on their side arms .
This is an old video of Gusler in his much younger days . Still a very good video though . You will see not only the forge process but the draw filing . What you don’t however see is how much work it took to get the barrel down to final shape .
Photo thanks to Bookie at Toad Hall
https://www.youtube.com/watch?v=lui6uNPcRPA
By the 1860’s arsenals were trying to drill bar stock vs. forge . The reason was that cartridge evolution was fast gaining ground , our arsenals could not keep up with demand and the Europeans were out producing us and importing cheaper then we could manufacture especially when it cam to the manufacturing guilds at Liege . Steel was also being used more and more vs the older iron
But what we were trying to implied was old technologies that had been discarded in favor of forging a tube as the blank . .
mass production was attempting to use large counter weights to force barrels onto the drilling machines .
This produced run out in the barrel stock just as with the forging process . When the barrels were then milled round what was produced was a substandard product that had thinner walls and often failed . Especially once harder barrel steel was being attempted .
The English however approached the issue from a differently . Their approach produced a drilled barrel with a much truer bore . One that could then be turned with out concern .
Thus we ended up with a complete British factory being purchase , moved board and nail to the US and the plant workers training our own workers here .
. Again I don’t do much concerning revolvers , but was not 1848 or there about when Colt hired Whitney to help produce his orders for the military ?
Prior to that as I understand it were they not fitted and assembled by hand ?
If that is trully the case then simply put , the shape of your cylinder could very well be a result of the manufacturing and fitting process of the time