Hi Kevin since the barrel length is less than 16inches, putting a "Stock" on it will require registration as a SBR "Short Barrel Rifle" and paying the associated $200 Tax Stamp fee. I would choose the KAK Brace here : google.com/search?q=ar+pistol+kak+brace&tbm=isch&source=iu&ictx=1&fir=E_aszsRD3t-kpM%253A%252CmIbsad_cr3kFSM%252C_&usg=AFrqEzdkLlZ0NchXpgM919dhAntgpS2DdQ&sa=X&ved=2ahUKEwjvv8S9_vbcAhWKPN8KHdn-BHMQ9QEwAXoECAAQBA#imgrc=jtsI_1eEl_JHUM:

You can not legally (lot of paperwork and money ) put a "stock" on this gun but you can put a "brace" on it here is one midwayusa.com/product/1018083310/sb-tactical-sbm4-pistol-stabilizing-brace-ar-15

Kevin since the barrel length is less than 16inches, putting a "Stock" on it will require registration as a SBR "Short Barrel Rifle" and paying the associated $200 Tax Stamp fee. I would choose the KAK Brace here : google.com/search?q=ar+pistol+kak+brace&tbm=isch&source=iu&ictx=1&fir=E_aszsRD3t-kpM%253A%252CmIbsad_cr3kFSM%252C_&usg=AFrqEzdkLlZ0NchXpgM919dhAntgpS2DdQ&sa=X&ved=2ahUKEwjvv8S9_vbcAhWKPN8KHdn-BHMQ9QEwAXoECAAQBA#imgrc=jtsI_1eEl_JHUM:

You can not put a "stock" on this gun but you can put a "brace" on it here is one midwayusa.com/product/1018083310/sb-tactical-sbm4-pistol-stabilizing-brace-ar-15