The problem is in deciding which comon rounds you want to match.
In Alaska the most common rifle is probably 30-06 i (West Virginia I would guess 30-30). However, you can't count on the people attacking you to be cooperative and carry what you do even if its the most common, 270, 7mm, 300 WM are all common as well.
Probably the most common pistol in semi auto is 40 caliber but again you are looking at people who could be armed with 357 or 45 and they may have revolvers.
I continue to think the best situation is where you have a decent amount of your own ammo for your gun and in all probability that will be more than enough to see you through.
More important is to form an immediate alliance with reliable neighbors and know who they are so you have a group for self defense. If you have extra guns you can "issue" to them and or share ammo or run reloads (in our case two of our reliable neighbors hunt and I would have no qualms about them carrying one of my 223s while on watch). It may not be the gun they use but they know how to use guns and a short education is all that is needed.
Typically if thugs encounter resistance they go elsewhere. They are not interested in dying and the residents are defending their families and property are willing to do so. Its not likely to take too much shooting to establish a safe zone.
In our case I would sacrifice the pickup to create a block so we do not have a through street. No one is moving that easily!
If you are not so lucky then plan accordingly but it is more difficult.
If it goes past that, we are probably in beyond deep trouble that no amount of guns and ammunition will get you out of (food, water and medicine becomes crisis issue inside a couple of weeks. )