Dan, you might also want to tell your friend to beware of what people will sell, because there are those out there that evidently just don't care that their peddling something that could cause serious injuries, or worse.
The first photo shows a barrel that was up for sale on a famous auction site, the stats are, bronze?, (my question mark) M 1841 6 pounder, 17-inches long, 1-inch bore, bore is cracked by breech. You'll notice the split was much wider than it now appears, look at the hammer marks on the top of the barrel. This cannon sold, and I'm guessing the buyer was going to try and braze the split and make a display model, but I don't know.
The second photo shows a later listing by the same seller only this time this champion of safety made some alterations, the bore diam. on this new casting was given as 15/16th's. I sent a message to this guy that went something like: Don't you realize that if someone, especially a kid gets hurt or killed by your gun exploding, that the silly disclaimer you attached to the listing isn't going to do anything to protect you from a legal backlash that will make the sound of your barrel going off sound like a ladyfinger popping, by comparison. Of course, this slouch went ahead and sold the barrel anyway, but I haven't seen any more of them come up for auction.
I saw this iron barrel on another forum, the owner said he had fired the piece hundreds a times before without any problems (well it only takes one time to alter your life forever). The owner thought this barrel was made of steel, (other members of that forum thought he was mistaken, and it was actually cast iron; I concur with their opinion) had a 1-inch bore and a .75-inch wall, he also said that it was loaded as usual with 450 grains of black powder (no grain size given) with a wad. This man is lucky this barrel just split like it did, it could have exploded like a fragment grenade. All I can say on this one is that anyone who is firing iron barrels of any kind that are not sleeved with properly constructed DOM steel liners are simply playing some other form of Russian roulette.