Brick Magazine from Argentina

Magazines come in two basic types, single or double stack, meaning rounds are stacked in a single row or slightly staggered, doubling capacity and creating wider magazine. This is model has been standared for pistols, submachine guns and rifles for 70+ years, with the occasional "stick magazine" aberration.

In 1938 however, Argentina decided 20 rounds of pistol caliber ammunition was not good enough. Weapons designers started building a 9mm Parabellum and .45 ACP chambered direct blowback SMG with a ultra-high capacity magazine in an all aluminum receiver.

The Hafdasa C-series was a submachine gun that could go from rifle to concealable compact SMG. The C-2 was the  tank-crew variant that completely removed the stock, followed by the C-4 (below) an all aluminum weapon for paratroopers with a folding stock or fixed and the Z-4 (above) with its monolithic fixed stock. 

The choice of aluminim receiver saved weight in a gun that could become very heavy when loaded with its hefty magazines.

The C-series of submachine guns had mammoth magazines holding 50 9mm rounds or 40 .45 ACP rounds. These magazines were two magazines encased in a single sheath that fed into the narrow receiver of the submachine gun. There were no reports of feed issues with this piggyback feed arrangement. 

Another design quirk of the Hafdasa C-series was the large spring loaded flap-style magazine well cover that protected the receiver from collecting debris in the field. The alumnium body of the Cseries also departed in a single color, choosing paint schemes of green, black and brown, another common sight on modern battlefield weapons.