I believe you can get FMP receivers that were stamped in Portugal and then welded here in the States and therefore considered a U.S. part. Be careful as the H&K kits I've seen have been so-so. I have both a Cetme -excellent/probably unfired kit, and a G-3 that is just fair-good with a good bore. I bought both kits and a Hesse receiver several years ago I but may go ahead and buy the U.S./FMP receivers. You just have to plug weld the receiver to the trunnion and then tig weld the cocking tube. Headspacing is different than most other rifles due to the locking rollers. A real nice site with plenty of great info (including build info)for both the H&K and Cetmes is http://www.cetme.org/mbr.html It's done by a great guy that goes by MWDG3.