Firearm with barrel clamp

A firearm, comprising:

• an upper receiver, including at least one barrel having a barrel axis, a barrel extension that can be connected to the barrel, a locking mechanism, and a firing pin mechanism;
• and
• a lower receiver, including at least one grip, a magazine, and a trigger mechanism;
• the firearm being configured so that when the firearm is in an assembled and ready-to-fire state the upper receiver and the lower receiver are connected to one another;
• wherein the barrel extension is connected directly to the upper receiver using a clamp, or the barrel extension is connected to the upper receiver via a seat using the clamp;
• wherein the barrel extension defines a prism, and the clamp defines corresponding prismatic guide surfaces running parallel to the barrel axis when the firearm is in the assembled and ready-to-fire state;
• the barrel extension is fastened on the upper receiver by a tension lever, the tension lever being rotatable in the upper receiver about a common axis of rotation that extends normal to a weapon center plane between two end positions corresponding to the assembled and ready-to-fire position and a dismantling position, the tension lever further including at least one clamping section, an elongated grip, and a cam formed on the tension lever;
• the clamp and the tension lever are connected by a pin along the common axis of rotation through at least one clamp hole or clamping lever hole that extends normal to the weapon center plane;
• when the firearm is in the assembled and ready-to-fire position, the barrel extension rests with a rear stop surface on the seat, when present, so that the barrel extension is clamped backwards by the cam against a forward direction of travel, and the clamping section biases the clamp in a vertical direction;
• and
• when the firearm is in the dismantling position, the clamping section and the cam lie entirely outside a path of movement of the barrel extension in the forward direction of travel.