I would much rather have a lease that does not have any reference to firearms in it than one that does. Especially if the lease asks 'Do you own a firearm?' Then states 'If not, you need to make sure and purchase one if you are gonna live in THESE apartments!!'
Seriously, as others have said, be discreet, and don't display or talk about them openly. That is just a good way to get your apartment broken into or hassled about the guns.