Abstract: The arrangement comprises a housing (1), a hopper (2) containing a powder and communicating with the interior of the housing (1), and a slide valve (11) having a drive (9) mounted inside the housing (1) and provided with a powder-metering cavity in the form of a recess (12).The housing has through passages for feeding compressed gas, and conveying the powder from the hopper (2) to the recess (12) and from the recess to the barrel. The slide valve (11) is arranged at the top part of the housing (1) and resiliently urged thereto in the zone of outlet holes of the passages. The arrangement also has a shut-off unit (18) connected to the slide valve (11) to block the outlet hole (8) of the passage for feeding the powder from the recess (12) to the barrel in one of extreme positions of the slide valve (11), in the other extreme position thereof the powder-metering cavity (12) communicates with the outlet hole (8) of the passage conveying the powder to the barrel.