I imported a bunch of flintlock BP rifle parts last year with no problem. I contacted the right fellow at the State Dept who read me the exemption for export permits for BP guns and parts. I talked to Clive Laws in Ottawa who confirmed I didn't need import permits for flintlock rilfes of parts thereof.
At Customs at Sarnia the gang of summer students who went through my car were more intersted in the catalogues and gun building course notes I had on my front seat than $1500 worth of flint locks, barrels, buttplates etc.
Again, I dealt with flintlock rifle parts. Not percussion or pistols.