I'm good enough that my cast will be without voids and inclusions, in the event I decide to cast around a core. Indeed, there will be machining necessary to perfect the bore, that's a given. There is also the method of shrink casting onto a thick walled industrial strength copper alloy manufactured sleeve (solid, no seams) with a polished bore. I stumbled upon some of this material some time ago and have been considering its application in this manner for several years.
Oh... in regard to making something beautiful, rather than plain (as in the M1857), that general era cannon was more admired aesthetically due the carriage and limber it had which was my main focus on finished quality. As for the cast, yeah... the barrel would have had ART applied to it, as well. I wasn't looking to capture a "perfect" reproduction of anything of antiquity. I'm looking to build myself a cannon purely for the fun of it and the opportunity to let out a BANG now and then when I feel fiesty, and to be a statement of my inner personality (as an artist). Not to mention the joy of being able to take it out to the inlet now and then and target practice with it at floating ice hunks in the winter months. Plus, it'd make 4th of July BBQ's at my house a literal "BLAST"!! No matter what cannon I make it won't be a perfect replica... it'll be a cherished member of my family (an heirloom) I intend to pass down to whichever boy of mine is most accurate with it. And to keep it, they'd have to either conceede to a loss (by not participating) or compete once a year with one another for top honors to keep the trophy for another year. Seemed like a good excuse for them to get together in life each year to have some fun together, wives, kids, grandkids, the whole lot of'em.