A rifle configured for firing a 7.62 x 39 mm round is provided. The rifle having: an upper receiver (58); a lower receiver (20), the upper receiver (58) being removably secured to the lower receiver (20), wherein the lower receiver (20) is configured to removably receive and secure a magazine (12) therein, the magazine being configured to hold at least 30 rounds of a 7.62 x 39 mm ammunition; and wherein a magazine well (18) of the lower receiver (20) is configured to receive an adapter (40) at a front (42) of the lower receiver (20).