Rail system for a firearm

A firearm comprising:

• a barrel of the firearm;
• a receiver of the firearm having a barrel receiving portion;
• a single barrel nut configured to:
• secure the barrel of the firearm to the firearm receiver;
• directly contact the barrel receiving portion of the firearm receiver of the firearm when secured;
• be disposed adjacent to the barrel of the firearm when secured;
• and
• have a non-circular outer surface when taken along an axis that is perpendicular to an axis of the barrel when secured to the firearm, the non-circular outer surface:
• being disposed on an opposing side of the single barrel nut with respect to an inner surface of the single barrel nut;
• and
• having a cavity included in a protrusion of the single barrel nut, the cavity being disposed on the opposing side of the single barrel nut;
• and
• a modular rail configured to:
• have an inner portion having a shape that is complementary to the single barrel nut such that the modular rail does not rotate about the axis of the barrel when the inner portion of the modular rail is mated to the outer surface of the single barrel nut;
• attach directly to the barrel nut when the inner portion of the modular rail is mated to the outer surface of the single barrel nut;
• and
• include a rotatable assembly configured to engage the cavity of the single barrel nut such that the modular rail does not move along the axis of the barrel, the rotatable assembly including a lever that is rotatable between at least two positions:
• a first of the positions being one in which a portion of the lever engages the cavity of the single barrel nut to prevent the rail from moving along the axis of the barrel effective to secure the modular rail to the firearm;
• and
• a second of the positions being one in which a portion of the lever does not engage the cavity of the single barrel nut and the modular rail is separable from the firearm.

An apparatus comprising:

• a barrel of a firearm;
• a firearm receiver of the firearm having a barrel receiving portion;
• a single barrel nut configured to:
• secure the barrel of the firearm;
• and
• have a non-circular outer surface when taken along an axis that is perpendicular to an axis of the barrel when secured to the firearm, the non-circular outer surface of the single barrel nut including a portion that is substantially concave in shape and extends inward toward an inner surface of the single barrel nut, the non-circular outer surface including a channel configured to align with a gas tube passage of the firearm receiver and a cavity approximately opposite of the channel, the cavity enabling the modular rail to be secured to the single barrel nut and the firearm receiver;
• and
• a modular rail having an inner portion having a shape that is complementary to the single barrel nut such that:
• the inner portion of the modular rail contacts the portion of the single barrel nut that is substantially concave in shape and extends inward toward the inner surface of the single barrel nut;
• and
• the modular rail does not rotate about the axis of the barrel when the inner portion of the modular rail is mated to the outer surface of the single barrel nut.