The answer is, it depends.
The list of "imported parts" that get counted are as mentioned above. I will trim the list to which parts are applicable to building a semi-auto 91 pattern rifle.
(1) Frames, receivers, receiver castings, forgings or stampings
(2) Barrels
(4) Mounting blocks (trunions)
(5) Muzzle attachments
(6) Bolts
(7) Bolt carriers
(8) Operating rods
(10) Trigger housings
(11) Triggers
(12) Hammers
(13) Sears
(15) Buttstocks
(16) Pistol grips
(17) Forearms, handguards
(18) Magazine bodies
(19) Followers
(20) Floorplates
The answer depends upon which parts you intend on using. If you're building a gun from a parts kit and are going to use that imported barrel & trunion, then you'll need two more "US" parts than if you were building a rifle with a US-made barrel and trunion (like JLD).
For compliance purposes, item #8 "operating rod" has been clarified to mean the charging handle on 91 pattern rifles, and they are (or at least were) available as US-made parts.
Also, since most folks won't be using US made versions of items # 18-20, those usually aren't applicable towards reducing the number of imported parts used, though I do have in my possession twenty US-made floorplates.
Bottom line is that some of those parts simply are not produced in the US and will count against you sicne you must use imported part. These include: #6, 7, 18 & 19. All of the rest of that list are available as US-made parts.
Hope that helps.