Old fashioned guns are not too implausible though, if they function and could be used as a side-arm then why not? Some people do use old weapons like revolvers.
The impression I get from the alien universe, atleast the first two is that they don't waste tech, ships are all fitted with old monitors and keyboards, granted the real reason is obviously due to the real life era and available tech but it does make you think about the in-universe reason for it all.