They probably don't stock clear lowers (since they're not commonplace) and there still is a chance that it will be confiscated by Border Services. In which case either it will be destroyed or they may let you appeal which may take upwards of a year or more and possibly still end in destruction.
Best bet is Age Verification on this site and buying things in country where it doesn't need to pass through Border Services.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE