Tom
I think some of our disagreement here, which is purely technical, may be a lack of info on our situations. I live in a closely built (about 15 feet between houses) subdivision with cinder block exterior walls. For this, I feel comfortable with low recoil #4 buck, but not .556 or a slug. You mentioned in another thread that you lived on the second floor. By this, I'm assuming an apartment. Given this, your choice of #6 shot seems reasonable, as you can't risk penetrating dry wall. I think we both agree that we would rather lose a gun fight than shoot the neighbor's kid with a stray round. Its all driven by the environment. You do the best you can with what you've got.
FQ13