My best experience with USPS was a I. Hollis SLNE that I bought from McDonald's Gunshop, in Australia. It arrived in absolutely perfect condition, in a not-very-substantial cardboard box with wadded up newspapers all around it ....... uninsured! (I know, that was luck)
Once had a hankering for a Westley Richards, high original condition double muzzleloader. A friend in Savannah got it coming from England, by UPS. It arrived in way too many pieces, if you get my drift. I was broken too ........ hearted, that is.
I've not had much luck using the USPS tracking system, either.
SRH
