It is only in America with the exception several countries that still have not recovered from war, where you can legally acquire all sorts of weaponry. These super destructive weaponry such as anti-tank rifles and anti tank cannons require the right licenses of course. With a sufficient background and money, one easily obtain many kinds of weapons. This is what makes America so great.
The Lahti L-39 is a World War 2 era weapon with a comically large magazine. This is because it fires 20mm armor piercing rounds to take out vehicles. This weapon was so effective it was used even after WW2, though most of it were sold as collectibles in the United States.