If you are building a weapon, you may use no more than ten of the following compliance parts made outside of the States. What I was trying, perhaps clumsily, to say, was that if he was going to alter the condition of the weapon to that of a pre-ban, he needs to alter ten of the compliance parts to be inline with 922r. That would mean adding ten more U.S. made parts. Ah, I see where you're going here.    The thing is, no rifle I'm aware of actually has  all 20  of those counted parts. The AK, for instance, has 16 counted parts so you'd only need to replace 6. A FAL, on the other hand, has 17 and thus you'd have to replace 7. The SKS is a bit easier to manage, with 15 counted parts.    Hence why it's more precise to talk about no more than 10 imported parts, rather than trying to talk about replacing X parts since it varies with the weapon system. The SKS, for example, has no barrel extension, mounting block, operating rod  (as far as ATF is concerned, even though it has a rod we tend to call an operating rod!) , pistol grip, or magazine floorplate as part of its design in its normal available configurations. Of course, if you had a Chinese SKS-D or SKS-M (which takes AK mags), the magazine floorplates would become an issue.