The only time you can have too much ammo is when you are swimming or on fire

 

Probably an 8mm Mauser (BRNO 98/29 or Yugo M48a). Source of image

I wonder how many Iranian families have some kind of a firearm squirreled away "just in case".

Sure would be nice if they had a supply of ammo. A gun without ammo is just a club. And a STEN, Owen or M3 (Grease-gun) and most handguns aren't even good clubs.

In rough order of the types of ammo that will be useful:

• 7.62X39mm Ruski
• 9mm Luger
• 7.62mm NATO/.308 Win
• 5.56mm NATO 
• 8mm Mauser
• 12 gauge 
• .45 ACP 
• 30.-06 Springfield
• 7.62X54mmR
• .303 British 

The Persian army used many different firearms from many different sources. Plus, the borders are incredibly porous. There is probably a lot of ancient ammo out there but it has not always been stored under the best of conditions.

8mm Mauser ammo from the former Yugoslavia

 

Same ammo on stripper clips

1974 and 1975 Lake City 7.62mm NATO cases