impossible to tell without any pictures and a better description , please add some pictures
cast iron or ??
bore diameter ?? and as many messurements as possible
probably not got a liner as you describes the bore as rough
cast iron barrels without liners should minimum hold 1,5 bore diameters in wall thickness in my opinion
so it would need a minimum of 2,6" in wall thickness to be "safe"
but even if they do I dont like cast iron without a liner
sounds like its cast with a core , thats an absolutely NO NO in cannons
that they realised already in the early 1700 ,
that it wasnt good and started to cast the barrels solid and drill the bore instead
cast iron is brittle, bronze at the other hand is tough
cast iron barrels shatter as a grenade when something happen
a bronze barrel would most probably just open up a crack along the bore axis
so I dont really likes the idea with cast iron barrels
if it got a rough bore Im not sure that its intended as a shooter
most probably its cast with a core , that makes it a typical garden ornament
be very sure about what it is before buyng it
could be just a garden ornament
one posibility could be to install a liner in it
but I just must say that you got a really nice wife , take good care about her
EDIT
sorry didnt see that about the golf ball size , if it got a 1,75" bore and just 1 to 1,5" walls its a big NO NO , DONT BUY IT
ITS DANGEROUS
cast iron in those proportions is not a cannon
ITS AN PIPE BOMB
JUST FORGET IT AND TELL THE GUY THAT OWNS THE SHOP
if he sells it and something happen he could be sued for everything he ownes and a little more
so think this over both 2 and 3 times before you buy it
I hope that you will save your money ( maybe your life also ) until you find something better
but you can find some very good cannon manufacturers among our sponsors
