Re: 7MM REM Mag what do you think??
Black powder is definitely a no no on an airplane. Best to contact your airline and see what you need to do to declare/package this stuff.
Remember, gunpowder is still considered an explosive. Having a bottle of it in a belly of an airplane may not be considered 'sporting' in this day and age.
I am sure the idea is for a trip north, not south to a Caribean wonderland.