suppressors are iffy best air on the safe side and not risk the importation
the the upper receiver for an m4 is fine its the lower that is restricted.
the rest of the parts you have listed are A-OK for importation.
mags are ok as long as there are no dummy rounds in them..
"You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here."