When it comes to firearms for sheltering in place, one concept is key: the layering of weapon coverage for your permanent position.
Your weapons should cover threats at extreme range (200 yards+), moderate range (200 yards down to 50 yards or less), close range (15 yards and in), and intimate range (closer that 3 feet). You don’t need a lot of guns; a minimum of four will suffice, but get more if you can afford them.
Requirements for such weapons, in addition to being from a military lineage, should be as follows.
Extreme Range Rifle
The 5.56mm does not get it for true extreme range shooting. It is accurate, but runs out of gas. For the AR-15 weapon system cartridge selection begins with the 6.8 SPC and goes up from there. The addition of an adequately powered scope sight is helpful, depending on the layout of your living area. If you won’t be shooting at extreme range, you may still need a caliber able to penetrate heavy cover or vehicles. For me, my M-1 Garand works well in that role (a Springfield M1A is as good as it gets), while my custom 6.8 SPC AR with scope works well at the extremes. Stay away from bolt guns if you can, as your threats may be numerous.
Moderate Range Rifle
Here is where the 5.56 ARs and 7.62×39 or 5.54×39 AKs, and the M1 carbine shine. If semi-autos are banned in your area, then your next best choice is a lever gun. Pump rifles are fine, but you can’t lay the forend on a solid rest and keep shooting. The .357 or .44 Magnum Marlin 1894 carbines come to mind here.
Close Range Long Gun
At 15 yards and in, the shotgun still shines, even though it has a reduced magazine capacity. If you have a semi-auto that runs good, the home is a good place to use it. You can even trick it out with high-capacity competition magazines or speed loading systems. Concealment is not an issue. Of course, your AKs and ARs are still good to go for this purpose, as are pistol-caliber carbines.
Intimate Range Weapon
Three feet and closer means pistols, weapons with bayonets mounted (as the ultimate weapon retention device), and combat tomahawks or large knives as last-ditch options. For pistols, I still err on the side of capacity. The 1911 or a classic combat revolver are great and reliable tools, but not when you are expecting a lot of company. If you can’t afford anything else, go with what you’ve got, and practice reloading.
Think about your defense mission at home and reevaluate what you have. If you don’t have a gun safe, get one, and fire-lined ones are the best. You don’t want marauders cleaning you out in advance of a major event. Know your local laws and practice, practice, practice.