It seems that historically, there was never a maximum number of domestic vs imported parts of rifles dictating legality. Is that 922r nonsense eventually going to be challenged?
It might be. No idea how good of a chance it stands. Things like import/export controls have a strong basis in history and text, even if stuff specific to firearms is a bit less (but there are still some good examples going back very far). Gun laws on businesses, imports, and exports are going to have a harder bar even with Bruen than individual restrictions. Granted, 922r is a pretty odd one.