After much research I have determined the following:
-For home defense a short 20 gauge (18 1/2)is best. Especially if a woman will shoot.
-Longer barrels are harder to manuver and easier to grab.
-finding the right round is the hard part.
Use the link I provided to narrow down the choices and then measure the possible shooting lines in your house. Then take your round choices to the range and test them at the same distances. You want a pattern no bigger then a mans chest at the longest distance. Hope I helped.
http://www.firearmstactical.com/briefs10.htm
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"It is easier to get out of jail then it is a morgue"
Live long and defend yourself!
John 3:16