When traveling "to and from" I use an oversized aluminum rifle case (suitcase type). Even the trained-apes that pass for baggage handler's with Alaska Airlines and ERA Aviation haven't been able to destroy the guns contained within, though they've created numerous dings in the case itself.
In the field, I use a blanket cover over the gun. When stopping for a break on the trail it allows me to shove the gun (in the cover) muzzle down into a snowbank rather than trying to find a tree or something to lean it against.
Historical evidence indicates that North West Trade Guns were placed in wool "sleaves" or covers prior to packing in crates for shipment. I've found a couple of journal entries describing guys removing the guns from their cases prior to use, so we do have evidence that they were carried in such a case in the field at times. The precise appearance of the early ones are unknown and subject to some speculation. I believe there is some artwork from the 1840s and later showing soft cases made from blankets, leather and probably other similar materials, but not a whole lot from earlier.
Swanny