US Patent 10415910 Offset feed magazine

An ammunition magazine for semiautomatic firearms has an opening at the end of a tube which is offset from the geometric center of the tube cross section and which is skewed about an axis extending lengthwise along the tube and through the geometrical center. Offset and skew of the opening are achieved by asymmetrically positioning the feed lips defining the opening relatively to the axis as well as angularly orienting the lips relatively to the bore of the tube.