Abstract: A system for connecting a barrel to an upper receiver of a modular rifle, the upper receiver having an upper receiver extension. The system comprises an upper receiver coupler having a first opening for receiving the upper receiver extension, which is removably secured in the first opening. The system includes a barrel coupler and a gas tube for attaching to a forward segment of the barrel, extending rearwardly along the barrel, passing through a second opening of the barrel coupler and coupled to a gas port that extends from the upper receiver and into the upper receiver coupler. The gas tube is shorter than the barrel. The barrel passes through and is removably secured within a third opening of the barrel coupler; passes through the first opening of the upper receiver coupler and into the upper receiver extension. The upper receiver coupler and the barrel coupler are removably connected.

Abstract: A kit for use with a modular weapon having a barrel and having an upper receiver defining a gas port and a barrel opening. The kit comprises an upper receiver plate for attaching to the upper receiver, and a barrel plate. The weapon barrel passes though concentric openings in the upper receiver plate and the barrel plate and is secured in the opening within the barrel plate. Another opening in the barrel plate receives a primary gas tube such that a rearward segment of the primary gas tube extends rearwardly from that opening and a forward segment of the primary gas tube extends forwardly from that opening. A forward end of a gas tube extension couples to a rearward end of the primary gas tube and a rearward end of the gas tube extension is received within the gas port when the kit is in use with the modular rifle.

Abstract: A kit for use with a modular weapon having a barrel and having an upper receiver defining a gas port and a barrel opening. The kit comprises an upper receiver plate for attaching to the upper receiver, and a barrel plate. The weapon barrel passes though concentric openings in the upper receiver plate and the barrel plate and is secured in the opening within the barrel plate. Another opening in the barrel plate receives a primary gas tube such that a rearward segment of the primary gas tube extends rearwardly from that opening and a forward segment of the primary gas tube extends forwardly from that opening. A forward end of a gas tube extension couples to a rearward end of the primary gas tube and a rearward end of the gas tube extension is received within the gas port when the kit is in use with the modular rifle.