Would he be able to ship it to himself?AR pistols are just like any pistol here. You no longer can buy the standard mags for it, have to settle for 10 rounders. If its shipped here it of course has to go to an FFL for the transfer. Like all hand guns there is a waiting period. Supposed to be no more than 10 days. Can often be a lot longer than that.
If you do not want to jump through the NFA hoops and make it an SBR, want it to stay a pistol, then no vertical fore grip. That's not WA law, that's fed law.