I often see questions form people asking why drum magazines are not more widely used - the BAR and the MP40/I in particular. People often view the box vs drum magazine question simply in terms of capacity - where the drum is obviously superior. However, there are several other elements to the question, and drums don't fare so well with most of them. Drum magazines are heavier, more expensive to make, and much more complicated to carry than simple box magazines. Drum magazines are a tempting idea, and they periodically pop up in military usage around the world. However, what I find telling is that virtually no military adopted two drums in a row. The US dropped the Thompson drums, the Finns went form a drum to a box magazine for the Suomi, the Soviets dropped the PPSh-41 drum in favor of a box mag on the PPS-43, and neither the Lewis nor DP was followed by another gun using their pan magazines.