@OP - Are you considering this a firearm or an explosive?
Also, what county do you live in?
As for I 1639 changes, SBRs are still safe -
RCW 9.41.190
Unlawful firearms—Exceptions. (Effective July 1, 2019.)
(2) It is not unlawful for a person to manufacture, own, buy, sell, loan, furnish, transport, assemble, or repair, or have in possession or under control, a short-barreled rifle, or any part designed or intended solely and exclusively for use in a short-barreled rifle or in converting a weapon into a short-barreled rifle, if the person is in compliance with applicable federal law.
RCW 9.41.220
Unlawful firearms and parts contraband. (Effective July 1, 2019.)
All machine guns, bump-fire stocks, short-barreled shotguns, or short-barreled rifles, or any part designed and intended solely and exclusively for use in a machine gun, short-barreled shotgun, or short-barreled rifle, or in converting a weapon into a machine gun, short-barreled shotgun, or short-barreled rifle, illegally held or illegally possessed are hereby declared to be contraband, and it shall be the duty of all peace officers, and/or any officer or member of the armed forces of the United States or the state of Washington, to seize said machine gun, bump-fire stock, short-barreled shotgun, or short-barreled rifle, or parts thereof, wherever and whenever found.