The 8008 609

OK, now you've made me dig out some references...

According to ISBN 951-0-00649-1, a Finnish translation of "A History of Warfare" by Field-Marshal Viscount Montgomery of Alamein, the first powder-fired artillery depicted in an European literary source seems to have used something resembling crossbow bolts, but there's a text from Firenze concerning iron balls for artillery. (both 1326, with powder-fired artillery of an uncertain type having been used at least in 1324 in Metz.)

According to ISBN 951-99414-7-9, a history of the Finnish army's School of Artillery, the first known piece in Sweden (1395) shot stone balls.

Iron was used first, whether wrought or cast isn't quite clear from these. The first pieces were pot-shaped with a narrower "throat" in the middle and every now and then the chamber could be a separate piece - at least in 1445 such a gun with two interchangeable chambers was inventoried in HSmeenlinna (Tavastehus).

Montgomery says that by the siege of Harfleur in 1415, cylindrical constructions had become common, but this obivously wasn't the case out here...

Subsequently bronze became an important material for cannons because a significant source of metal was church bells and candelabrae, All-copper pieces were tried in Sweden but they "proved impractical".

As for the Turkish artillery at the siege of Constantinople, they used at least stone balls, up to 500 kg in weight. But some of the guns were produced elsewhere - the 500 kg gun was made in Adrianople and pulled to the siege lines by 60 oxen.

By the mid-1500s iron was considered an inferior material, but it was much cheaper, and the ballista was still occasionally tactically more advantageous. (Olofsborg 1553: 5 bronze-brbutt guns, one of which shot stone balls, and 120 iron guns.)

-- #Not speaking for my employer. No warranty. YMMV.