NEVER use this rifle with the 156- or 160-grain slugs, NOR with the Norma-Oslo sealing ammunition which is so common in 50-round boxes on the East Coast; it was designed specifically for the 1941 load, which used a 139.
The rifles were deliberately overgassed in order that they would function at temperatures of minus-40.
The direct-impingement non-adjustable gas system means that you CAN install a set-screw at the Gas Block in order to LIMIT the amount of gas getting to the Carrier.
Swedish Armourers had a KIT consisting of a special tool and a range of Gas Orifices which were to be installed in the Exhaust end of the Gas Tube. These kits seem never to have been surplussed and are about as common as nice-smelling Lutefisk.
Nice thing about this oddball rifle is that, once you get it running, it is likely the most accurate out-of-the-box semi-auto rifle you will ever find.