There's a firearms auction coming up in March at the well-known firm of James D. Julia Inc. I don't think I've ever seen so many 'grail guns' available before! Here are only a few of the remarkable firearms for sale.
There are many more rare firearms to be seen at the link. It's like Mecca for firearms enthusiasts . . . a very expensive Mecca, unfortunately!
(I think Murphy's Law should buy that Spanish blackpowder mortar. He can use it to fire a basket of tennis balls from his porch, to be chased down and returned by his dogs. As a bonus, he might be able to bounce the balls noisily off the roofs of some of his more annoying neighbors!)