Jeff is right there. Recently I was asked to make up about 12 FN/L1A1 'rifles from captured Argentinian FN's other odds and sods from various FN's plus a large assortment of L1A1 bits. And you'd be suprised at what parts actually interchanged. The only part that beat me at first was that I couldn't use L1A1 cocking handles in the FN bodies that I had. But as soon as I'd bevelled the edges of the slides, they fitted a treat. Then they wouldn't fully fols until I took off the redundant metal from where the non folding handle went. All worked perfectly.