Abstract: A semi-rigid locking system for a firearm is described. The locking mechanism has a breech block which is locked with the stock and which can be released by a spring-biased control member. The breech block has at least one bore which receives a locking element supported for radial movement in the bore. When the breech block is in the locked position, the locking element is supported by the control member and engages the stationary locking surface. When the breech block is in the release position, the locking element is released by the control member which moves in the breech block parallel to the breech block. The locking element does then also no longer engage the locking surface and can move freely. The control member has control surfaces which are inclined at different angles with respect to its axis, while the locking element has control surfaces which are complementary to the control surfaces of the control member.

Abstract: A system for changing the barrel of a firearm includes a firearm that has a stock having a trigger mounted thereon and a housing part removably attached to the stock in a fixed operative position. The housing part has a sighting mechanism on its upper side. A barrel is mounted in the housing part and a breech block is disposed in the housing part, which travels rearward on firing and cooperates with a locking system mounted in the housing part. A closing spring surrounds the barrel and means are provided for connecting the closing spring to the breech block. A firing pin is reciprocally received within the breech block. Also provided is means for removably retaining the barrel, closing spring, breech block, connecting means, and locking system within the housing part. A releasable key means, which holds the housing part in the fixed operative position, has a release position to remove the housing part in a direction substantially transverse thereto.