Abstract: This invention relates to a breech assembly of a gun adapted to fire caseless charges, ignited and enhanced with electrothermal chemical (ETC) charges. The gun utilizes charges as propellant and a plasma generator cartridge (PGC) for generating plasma when an electrical current is applied thereto. The breech assembly comprises a breech ring, a tilting block assembly, with a spindle installed and a sliding block for supporting or locking the tilting block assembly in a sealed position. The tilting block assembly is movable between a PGC firing orientation and a PGC loading/removal orientation. The breech assembly further includes a crank means, which includes a guide means for rotating the tilting block assembly from the PGC firing orientation to the PGC loading/removal orientation.