Technical answer, maybe. The ordinance doesn't say firearms in that particular code, it says "dangerous weapon". I don't see where it defines "dangerous weapon" any further.
Realistic answer, you're fine. If you're being safe and not shooting the neighbor's cat or something, its a non-issue. I have not once seen a citation issued under the ordinance, and only once have I warned someone about the ordinance (guy shooting a handgun into a wooded area with an apartment complex on the other side of the wooded area. No way a bullet could have gotten through the trees, but still a stupid place to shoot since you could access the woods from the other side).
I've also heard a crossbow/bow is also verboten because its written so vague to include "spring powered" weapons. Technically, at least long bows are springs. its not too far of a stretch to consider a compound also spring powered.
But I think BBI is right. Just dont **** off your neighbors (or do it where a JBT can see you as he drives by on patrol) and you'll be OK.
Sec. 451-3. Discharge of weapons across public ways.
It shall be unlawful to shoot across or upon any public street or place, or toward a public way from any private premises, any bullet, pellet, missile or object impelled from any gun, pistol or weapon operated by means of any explosive charge, or by springs, air pressure or other means, or impelled from a slingshot, or any other device having force directed by the user thereof.
In typical fashion of laws, take it as you see it, and hope someone smarter than you doesnt take you to court over it.
Don't know on the legality, but I grew up in Marion county and always shot my pellet gun in my backyard. We had woods behind us, and a wood pile behind my targets. I know that doesn't help you. I was too young to even begin thinking about legality of it. As far as I was concerned, my parents said it was ok, and that was good enough for me.
I mean, I DO NOT think a pellet gun is a firearm, I like to go by ACTUAL definitions, dont misunderstand me. Im saying Im pretty sure the gubment does...