I was recently given a S&W Model 916A 12 gauge pump shotgun with a 3 inch chamber (previously owned but in never-fired mint condition)that I would like to use for home defense. I own many rifles, pistols and revolvers, but never owned a shotgun before and know nothing whatsoever about them -- and I mean nothing. For example, can I use a 2 3/4" shell, or are there 3" shells I am supposed to use. Also, what kind of load should I use. I'm not overly concerned with a big spread as I am confident that I'll hit what I aim at, but I also don't want anything that has too much penetration as to go through my kids bedroom walls. I still want decent stopping power though. Any thoughts, insights or recommendations would be greatly appreciated. Thanks, Anthony.