I always put them on a different 4457, (gamesmanship, the system teaches creativity) not a single person, this side or that side of the Atlantic has ever even known I have a can, or cans, in my rifle box. The only thing anyone has ever cared about is a rifle serial number. Having said that, the cans are not on the rifles, they are in a separate pouch with other items, sling, bipod, etc. I also have a copies of my tax stamps with me, just in case. Is CBP searching everything, or is that being done in South Africa? Take your can, everyone within earshot will appreciate it. I'll be in Limpopo this August, rifles will be properly silenced.