I could get real deep in this subject.
To make it short, all the comments above are true about all three, USPS, UPS, & Fed Ex.
What helped me . . . I starting double packing the contents and in many cases double boxing. I spend a fortune on heavy reinforced shipping tape. If the contents are loosely packed, the package is going to get crushed. On a real important items or delicate items, wrap the content in plastic and spray the inside void areas with non-expanding foam. They make shipping foam just for this. This method really works. Since I started paying more attention to packaging, I have just about wiped out my issues with all three companies. Oh, NEVER use padded envelopes. Barrel nuts or recoil lugs will most likely never make it.
Yes, I hate doing it, but in the long run for us, it's cheaper.
Bullet shipments are the worst, 500 plus, they will destroy a cardboard box. I have ordered bullets from individuals who put them in baggies and filled the remainder of the box with foam peanuts. This is not going to work. Any piece of metal, including a die will puncture a cardboard box, or destroy a padded envelope. Just look at the tracking information and imagine your package bouncing around in the back of the shipping truck, probably under many other packages.
I had one of the companies this year flipped a "new" CNC and rendered it useless. It was in the same truck your small packages were in. I wonder how many were under my machine.
USPS flat rate boxes, you would not believe what people try to stuff in these boxes. USPS finally put a weight limit on the boxes, they had to. I sometimes take my delicate items packed in an envelope or small box. I spray foam in a larger flat rate box and insert the smaller package, then fill the remainder of the void with foam. It works, and part is delivered undamaged. Why, the claim process is almost a joke with all three companies.
ORM-D items are "required" to be shipped in heavily reinforced containers doubled walled. They still get a little damage, but usually survive.
JMO, Dennis, and yes, it's a sore subject. Bottom line, just make sure you package is well reinforced, packed tight, and has insurance on it.