For revolvers check hibernia's main building first since it's guaranteed there and while exploring mystery lake look around trapper's cabin and camp office, good spots under beds or behind storage. Coastal highway's got some nice chances especially around quonset where they hide behind counters but no promises except for hibernia.

Distress pistols are way easier since they're always in the same spots - climb timberwolf mountain for one in the plane wreck, rappel down the ravine near the railcar, or check bleak inlet's fallen lighthouse roof. Ash canyon's gold mine is worth checking too if you're nearby, just watch your step up there.

Remember no guns spawn on interloper difficulty at all, and lower difficulties mean less stuff around. Maybe interesting: corpses in coastal highway and mystery lake often have good loot so keep an eye out while exploring those regions, especially if you're desperate for weapons. The distress pistols won't move though so you can always count on those fixed spots when you need one.