The edit feature here, is irritating!!
Updated and added too.
What are the rules pertaining to AR pistol laws in WA? Any firearm that started life as a rifle and has an OAL under 26" = SBR. Doesn't matter if it has a stock, brace, or just a grip. Felony without a tax stamp. Any firearm that started life as a rifle and has a barrel under 16" = SBR. Doesn't matter if it has a stock, brace, or just a grip. Felony without a tax stamp. Brace with no foregrip = pistol. Barrel length doesn't matter. Legal. Brace + angled foregrip = pistol. Legal. Brace + vertical foregrip with overall length under 26 inches (not including brace length and muzzle device) = AOW. Felony without a tax stamp. Brace + vertical foregrip with overall length over 26 inches (not including brace length and muzzle device) = firearm. Legal. Stock with overall length under 26 inches = SBR. Barrel length doesn't matter. Felony without a tax stamp. Stock + rifled barrel under 16 inches = SBR. OAL doesn't matter. Felony without a tax stamp. Stock + rifled barrel over 16 inches and overall length more than 26 inches = rifle. Legal. _____________________________________ Washington really has no laws regarding AR pistols. As another stated, if the barrel length is less than 16", or if it is designed to be shot with one hand it's a pistol. Notice the OR. Just follow ATF rules if you want to be safe from fed boy hassles. But even then there's a 9th district ruling(we're 9th district) that appears to say VFG are legal on pistols. IIRC it's US v Fix. _____________________________________ Well in that case since you said "the “arm brace” can’t be changed out" I assume it's has a brace now and has always been a pistol? In that case you're all good, just don't add a VFG unless it has an overall length as measured by the ATF of 26". I'm not sure what you mean "changed out" on the brace, you can change for a different brace, take the brace off, etc. You just can't put on a stock or modify the brace to make less bracey or more stocky. I suggest if you travel with it I suggest you make copies of a couple documents and keep them with you. 1. Whatever best ATF letter applies to your brace. 2. A copy of [RCW 9.41.010](https://app.leg.wa.gov/rcw/default.aspx?cite=9.41.010) (23) Makes me wonder if it's possible to get a copy of a 4473.