A Stock MUST NOT be able to be fitted to a PISTOL. OTHERWISE, IT IS AN SBR!
A PISTOL MUST have means such that a STOCK CANNOT be readily applied to the system. An SBR is a CLASS-III weapon. It must be transferred and applied for with a TAX STAMP like a machine gun transfer. DO NOT kid yourself. If you are found with an SBR without legal remedy such as a TAX STAMP, there will be serious penalties imposed.