Gas-operated firearms, in which the gas system guides gas selectively from the gas removal bore to a gas pipe, with a platelet, movable between at least two positions in the gas system. The platelet may be pivotable about a pivot axis pin. A stop pin, parallel to the pivot axis pin, may protrude into a stop bore of the platelet, thus delimiting the pivoting. The platelet may have at least two recessed catch positions, into which a catch, under the effect of a catch spring, optionally engages, provided that the gas through-bore associated with the catch comes to rest in alignment between the gas bores when the catch engages in one of the recesses.