Who started the "USPS is better" myth?
There doesn't seem to many quantitative comparisons of shipping reliability, in the only 2 I've seen, the experiences of a couple of companies one had USPS losses about 20% worse than UPS, for the other, which didn't post the actual numbers, USPS was 200% worse, but these are limited samples.
I've never had a loss shipping hundreds of firearms either UPS or Fedex. My only loss has been one gunstock sent Priority Mail, the last time - ever - that I shipped USPS, mainly because even if they delivered undamaged their tracking stinks.
There is an insurance problem with the commercial carriers in that they wont cover unusual items or those which can't be duplicated for more than a nominal amount, and this sometimes catches those losing an expensive gun. However Collectors Insurance policies include coverage for full value during shipping.
