Another alternative maybe worth mentioning for a gun without swivels is a light, flexible gunslip with a shoulder strap https://www.connecticutshotgun.com/product/traditional-english-gun-slip-2/

These can be rolled up and carried in a vest or bag while actively hunting and broken out for the trek in or out of the field. Downside is the gun is harder to get to than carried or slung. but even a very thin light slip offers extra protection.