Hugo Simais designed and applied for the patent of the world's first double-row single-entry in-line magazine, which can hold 20 9 mm Barabem pistols. Hugo Simes tried to use this magazine on MP 18 I submachine gun, but the German Firearms Inspection Committee asked Hugo Simes to equip MP 18 I submachine gun with P08 spiral drum with a capacity of 32 rounds. The purpose of this decision is to make up for the shortage of ammunition capacity of MP 18 I submachine gun. But another problem is that MP 18 I submachine gun equipped with P08 spiral drum is not conducive to the long-range attack of troops.
The spiral drum of P08 pistol is fragile, easy to destroy, expensive and complicated to manufacture. The production relies too much on manual trimming and needs tools for loading. What is even more paradoxical is that it is a product of Lugar Company, and its magazine with 8 rounds of ammunition capacity cannot be loaded into MP 18 I submachine gun in an emergency because of the protrusion on the magazine ... which has many shortcomings. Although Hugo Simes's double-row single-entry magazine is not as good as his father's, in view of the bureaucracy of the German Firearms Inspection Commission, it is required that the MP 18 I submachine gun must use Luger's P08 snail drum, and the angle between the barrel axis and the magazine slot axis must be designed to be the same as that of the P08 pistol. The more serious problem is that the ammunition supply port of MP 18 I submachine gun is located on the left side of the gun body. Therefore, after inserting the spiral drum of P08 pistol, the center of mass of the gun body moves to the left seriously, and the consequences can be imagined.
In order to reduce the weight of the gun, balance the center of mass and shorten the length of the gun body, Hugo Simes requires that the interface between the bullet and the drum must be equipped with a strengthening sleeve. Because if there is no reinforcing sleeve, the roller will lose its positioning point in the normal feeding position, and then it will be inserted into the gun too deeply, and the gun will not work.