We do have to register our guns, at least in PA.
Some states like NY require your carry permit to list EVERY gun you own. I recently saw a retired cop's permit from NY and it took the front and back of one card and a second card front to list his collection.
Every time he buys another, he has to pay the State of NY another fee for an updated card.
The bureaucracy of ammo registration would be impossible. President Obama has insinuated about it but his intentions would be to prevent anyone from being able to get any ammo, not to track it or for safety reasons. So instead, he's just having DHS buy billions of rounds and literally dry up the supply in the popular calibers. It's very difficult to find some types and when you do, the price has gone sky high. It's a very underhanded way of implementing gun control without having to write or follow laws.
Also, by "those types"...you can't deny Baltimore or any major city has a higher criminal element. The chances of getting mugged or carjacked there is much greater than if you drive to a rural town or even smaller city like Hagerstown or Frederick. You can't really argue that, can you? You do have to be aware of your surroundings a bit more in a city. That's all I was saying. I live in the country and work in the city so I see both words daily.