I shipped 4 boxes of Quickloads for my Hawaii trip a few months ago via USPS Priority Mail in their Flat Rate box for only $8.95, and shipped it back to myself via the same, so for a total of $18 not only did I not worry about x-rays but also didn't have to hand carry those 4 boxes.
The box of TXP320 I had in my camera bag, as well as loaded film holders, was fine as well...
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