I think Gatling gun and friends are definately considered "early" machine guns, in that they fulfill what is probably the most important distinctive feature of

I think Gatling gun and friends are definately considered "early" machine guns, in that they fulfill what is probably the most important distinctive feature of machine guns - relatively sustained periods of high rate of fire. There are lots of ways to argue about what exactly defines a machine gun, but if we take the perspective of what it's like to be shot at by one, I think we can say that Gatling guns and friends are close enough that I don't really think it matters. This helps highlight juts HOW MUCH BETTER the Maxim gun was compared to everything before it though.