If you are planning on revolvers .38, .357 (depending on what kind of ammo you plan to use and where you live) , .44 special,and .45LC are all good home defense calibers. As far as barrel length goes the 3 - 4inch barrel in my opinion is good...6in is to much. However if you are planning on a semi-auto .380, .9mm, .357sig and .45 are all good calibers but as far as semi's go they require more time on the range depending on which one you plan to get. I hear Glocks are the easiest semi to use.