I had more than one firefight in mind too.I would envision most shoot-outs using a shotgun wouldn”t go past 15 or 20 rounds.On our own out here in the country I don’t know how long we would last or how the threats would be presented.One or two hostiles at a time or maybe 10 or more.I’m fairly proficient with all my weapons,but having no intel for threat assessment would suck.
If you luck out, no one will come, and it will be business as usual with an edge.
City folks would have a bad time of it.
I have great neighbors out here in my country location.All of them are armed.No one will mess with our neighborhood without tanks and full auto weaponry. There is nothing here worth that effort.
Go past around 60- 75 rounds with plastic-cased shotgun buckshot or slug ammunition, and you'll find that the barrel can become hot enough to melt the plastic cases. It becomes quite possible to chamber a round, then have it either stick in the chamber, or leave sufficient plastic residue to prevent the chambering of a followup round.
There are a few things you can do to help matters, to include leaving the chamber open between shots if things go beyond a dozen or so rounds, to get all the cooling possible. And of course the composition of the plastic used in differing brands of ammunition varies, so some can be expected to do better than others, and your particular gun may have a tighter or looser chamber than others.
Check out what some of the trap/skeeo shooters who fire 200-round strings use- but remember that their lighter target loads don't generate the power, recoil, heat or pressure of full-house buckshot and slug loadings.