Recalibrating the system for laser guns is one way to go (and the way I'd prefer), but not the only way. Several sci-fi settings for 5e such as Dark Matter from Mage Hand Press, just balance all that stuff against core 5e assumptions.I am open-minded about that idea. It is possible, but the high-tech firearms would force to recalculate the challenging rating of the encounters. With the right weapon an enemy, a giant beast or a combat vehicle, could be killed or destroyed with only one shot. Even a civilian vehicle could be used to run over a horde of zombies. I guess the easiest option could be a videogame using a variant version of the d20 system. I feel a lot of curiosity of a G.I.Joe+Cobra-la mash-up version set in Gamma World. Why not to ask IDW to publish a comic about that?
Why Gamma World? If you want it can be child-friendly with mutant antropomorphic animals, or grimmer/mature style like Heavy Metal cartoon movie.
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I swear I'm not a shill for MHP, it just happened to come up.