Everybody probably knows this,but.....
Reliability is an essential. Before one dedicates am arm to defense, one should and must ensure that the weapon and ammo are compatible,effective and reliable.
With shotguns, this means that one should fire maybeso 100 rounds or more of ammo of choice w/o ANY glitches before betting the lives of you and family on it.New shotguns, double that, at least.
Some shotguns are reputable for dependability, like the Auto-5,870, 97,37 and 12. Even with these, a break in period and use should precede assignment to HD status.
Now this doesn't mean you have to go out and punish yourself firing off all 100 rounds of 3 inch,15 pellet 00 today. Maybe over the course of a coupla weekends, interspersed with clays or whatever and practice ammo.And, for that matter, one doesn't need 15 pellet 00 to work. Use some sense instead of having to reach for the anti-inflammatories.