No, really. I'm serious - read this article from the Atlanta Journal-Constitution:
When General William T. Sherman rode through in 1864, folks got out of the way; and hundreds of Kennesaw State University students were evacuated from a classroom Monday because of two live cannonballs on campus.
They were not uncovered during construction or an archeological dig, but had been gathering dust in a display case for three years on the third floor of the Social Sciences building. The room had limited access.
So. How do I know my civil-war era cannonball looks like this on the inside...

And not this...

When all I see is this?

Well, you'll need to look for this.

At least one (if it was a really old deactivation - or done by an idiot) and preferably two holes. This indicates that someone (who may have been an idiot) drilled the round and flushed it. Two holes does a *much* better flush job. Of course, you probably should have the *other* guy handle it... not that it will help much if it does go off. And even when you've got a lot of experience, they can still go off. We've not seen the last casualty from the Civil War yet.
If you don't know what you're looking at, leave it be - whether it's on the ground or at a show. If you run across one "in the wild" tell the authorities and let them deal with it. Especially if you can see a fuze. But don't assume that because you don't see one - there isn't one underneath what you can see.
If you simply must own one, unless you're dealing with a person you know to be knowledgeable and honest, the risks just aren't worth it, and you can get good repros for a display.
And don't go poking around in those holes (I know some of you are going to try) unless you do it with a non-sparking probe, such as wood, brass, or copper. Because you *don't* know how well they did their job. And remember - it also matters where it came from. Relics recovered from national battlefield parks are illegal. I got the ones I have from a reputable dealer with a storefront and raft of books to his credit - who could attest to where the rounds were recovered.
H/t Toluca Nole for the article link.



Several of my students lived in the Dallas Line Campaign vicinity, and said they had found various artifacts around their houses. I was always nervous when they wanted to bring them in to show me, for this very specific reason.
I'd love to know which of the KSU profs these belonged to - I have a idea I know which one!
BK: " Well lets go over plan again. Double check everything"
Again load fire get the shot report. Ordince disposal recovers the unit for the science boys. Carefully. Look for round 1 no luck. As it was an active range I guess they weren"t too concerned.
Two weeks later policing the road the OP's use to get to their posts, we spot a Blue object lying beside a fir bough 3 yds. off the trak, its the round, and it looks like new except You could make out the striations on the copper(?) ring.. Call Ord Disp. Out they come. A newby Lt.
"Ok I'll just defuze it and transport it to HQ." says he
"not so fast Sir. SOP detonate all rounds. This one goes up before it goes in." BSM
says," besides my gun my round, and we're following SOP"
"Well ok, but I'm sure Hq would like the whole thing"
BSM and Ord tech attach a 50' cord and command wire to the det charge throw it over the round catch it, then drag the demo along the ground to the round from the other side. It nestles up to the round.
"OK sir, lets attach th" KA FOO?ING BLAM
Left the much wisened lt with the remains. Amen
Joe - another favorite (this time of unscrupulous/ignorant merchants) - iron balls used in mining for crushing ore being sold as grape shot or Revolutionary War cannonballs.