I594 was not about the "background check loophole " its the first step to take the guns away from the leagal gun owners by disguising the word transfer to confuse and mislead most voters a powder acuated nail gun  and others like it would now be illegal to "Transfer" or purchase due to the wording on I594 
Sec. 2. RCW 9.41.010 and 2013 c 183 s 2 are each amended to read
as follows:
(9) "Firearm" means a weapon or device from which a projectile or
projectiles may be fired by an explosive such as gunpowder.
"Champions of Initiative 594, basking in its landslide victory, delivered a post-election message on Wednesday: We’re not done yet."