I'll help you out here as an Illinois resident. A firearm must be transported, unloaded, in a case specifically designed for firearms. It does not have to be a lockable case.

As far as the ammunition goes I would not recommend carrying a loaded magazine in the case with the firearm. As someone said earlier different cops interpret things differently. Whether their interpretation is correct or not if they cite you for carrying a loaded magazine with the firearm because in their opinion it is then a loaded firearm ,it will wind you up in court and be a hassle that could've been easily avoided. It would also drop an arrest on your record and whether found innocent in court or not that record of arrest will be with you probably for life.