Defensive Gun in an Apartment
I am going to be moving into an apartment next month. It is a 3 story Town house. The Bedrooms and a bathroom are on the top floor. My Problem lies in planning for a home invasion. I don't know what the two walls that connect my unit to the other two surrounding mine are made of. I contacted the landlord to find out but he wasn't sure. He said he'd try and find out. Best case scenario is that there is a Concrete firewall separating the units. Worst case is that there is 4 to 6 layers with a possible sound deadening material. From looking at the Box 'O Truth Website, I don't know what kind of ammunition I could use without possibly injuring a neighbor. The rooms are not very big and I would very likely hit a sleeping neighbor.
I know that Bird Shot and Frangible Rounds are very very frowned upon as Defensive Loads but I don't see many other options.
I'm looking for suggestions pertaining to the Wall being made of 6 Sheets of drywall. I had someone in the next unit bang on the wall and I don't think there's concrete.
Weapons to choose from are an AR-15, 12 ga, 20 ga, or a 9mm
Thanks in Advance!