For this very reason, the adventurers used to engage in regular combat with the Green Skin Orcs at distances within a hundred meters.
Between fifty and a hundred meters, the adventurers had some firepower advantage, but the Green Skins were able to rely on their thick hides to charge within fifty meters, at which point exchanging fire was no contest at all.
One of their shots could blow apart a person, while our side's puny guns needed to pour a hundred bullets to kill a single Green Skin, how could we fight like that?
Moreover, once the Green Skins got within fifty meters, aside from shooting, their steps wouldn't stop, and they would charge even closer to take advantage of the high power but low accuracy of their guns.
Or more directly, they'd get into melee range and resolve the battle with cold weapons.