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