Yes the only difference is the stock. A SBR is a short barreled rifle. The ATF defines a RIFLE as a weapon that is shoulder fired with a barrel of at least 16" and a OAL ( over All Length ) of at least 26". Thus in reality the ONLY difference between a ar15 pistol and a SBR is the ability to fire from the shoulder IE stock. Buy a pistol send in the form 1 when the stamp comes in have it engraved and buy a stock for it.I am interested in a SBR, but I was trying to fing out more details of the tax stam info. If it was built as a "pistol" AR does it still need to have the $200 tax stamp? Is the only difference the stock?