These people seem to have one of everything...
Yep. Somebody once said that consistancy is the hobgoblin of small minds.
It's true that having about half of the hardware be of a standard/uniform type simplifies training and logistics, but for small units depending on cached supplies, whether regulars or militia, there's also an advantage to be had in having a variety of usable calibers so that a shortage of any one is not a critical shortfall. It's to be expected that as ammo is expended, some pickup weapons become available, with the ammunition in part supplying the weapon so recovered, and a portion cross-leveled to other users already so equipped. THe Finns in their 1939 war against the million and a half Soviet invaders were masters in this respect, simply resupplying from the enemy dead.
The people from Michigan in the BDUs don't look to be that badly off: 3 M16 variants, 2 in the 7,62 Soviet M43, 3 questionable or unequipped, and one with a probable .22 rimfire, which has some very interesting uses at night. And at least one 840 round ammo can visible. Hopefully there'd be some LAWS or M136 AT4's carried by those appearing discretely unequipped, maybe a SAW or a couple of scoped long rifles as well.
Others elsewhere might find a different mix more suitable, as per the following *Magnificent Seven*: