If room-clearing is something you think may be on the agenda, it might be worth looking at a bullpup option like the Tavor.
As mentioned above, you will lose a lot of velocity with an 11" barrel and velocity is what 5.56 has going for it in terminal performance.
As mentioned above, you will lose a lot of velocity with an 11" barrel and velocity is what 5.56 has going for it in terminal performance.