RCW 9.41.010
(16) "Large capacity magazine" means an ammunition feeding device with the capacity to accept more than 10 rounds of ammunition, or any conversion kit, part, or combination of parts, from which such a device can be assembled if those parts are in possession of or under the control of the same person, but shall not be construed to include any of the following:
(a) An ammunition feeding device that has been permanently altered so that it cannot accommodate more than 10 rounds of ammunition;