Ahhhh...errrrr.... hummmmm. the HK 91 receiver is quite complex requiring a Jig, welding gear, measuring equipment, prints, and flats made to specifications. Its not a fold and weld deal...thats the Grease gun. Greek or Pork-and- cheese flats are the only ones I know of that are good...although I've heard the Turkish meet specs...but thats hear say.