while you have a complaint, i have shipped usps for over 12 years for my prior company.
shipping LEAD and brass
you must pack SOLID. no room for movement. a box of bullets bouncing around on the inside will tear your box apart.
wrapped in tape.
heavy box ? strapping tape
never lost a lead shipment, nor a brass shipment.
post office hated me.
70 lb limit flat rate $15, i would ship 60lb s,
sometimes 4 or 5 boxes on the same day.
brass 2500 pc of 45 acp in a large flat rate box , once sent 10 boxes to the same guy on one day.
Bingo!
I've been in the shipping industry for 15 years and that is the best advice you'll ever get in regards to shipping. Internal movement is what destroys packages more than anything. Items like bullets and brass shift and settle during shipment so even if it was packed tight when you taped it up, it won't be after a ride in the back of a truck.
Before you ever hand a package over to ANY carrier, ask yourself if you'd be comfortable dropping it onto a concrete floor from at least 60" off the ground. If the answer is no, repack it. The most successful shippers I deal with understand that spending money on a quality pack job is a lot cheaper than eating the cost of damaged/lost product resulting from improper packaging.
Edit to add: It's worth pointing out that the package obviously got wet as well. Just something else to account for when packaging items.