Inefficient magazine capacity?

This website sells a popular 50 round drum.
As you can see from the picture, the bullets only occupy a very small percentage of the space inside the drum.
Meanwhile, the American-180 drum holds 270 rounds! and the drum is not that much bigger than the 50 round one. So why cant someone invent a 270 round drum that can be inserted into a regular firearm like the 50 round one?

Let's block ads! (Why?)

Inefficient magazine capacity?