If they're quite valuable I'd ship them insured via common carrier like Fedex or UPS to your destination. As seen by oodles of posts here there is no foolproof way to avoid unscrupulous airline or government employees.

The only other approach which comes to mind is the unloaded flare gun trick where you put said 'weapon' in your bag & declare it to the airlines as a firearm. Makes it illegal for others to open the case outside of your presence but might add a ton of hassle to your trip. Search the forum for more detail (and make sure said item isn't illegal at your final destination or in-transit stops).