Well, if the Iranians can manufacture the armor-piercing ammo, they could make their own rifles- it is not THAT difficult. But why on earth make their job easier?
look at it this way, you sell the enemy 800 guns. now, they don't need to make their own. you invade them, and you know exactly what you're looking for.
you refuse to sell to them, so they make their own. now, how many do you suppose they have? how many will they make to replace what you took?