As to powder, do remember that the military ALWAYS uses the fastest powder they can get away with: less weight to carry, less tonnage to buy.
Swedish method of controlling the uncontrollable Ljungmann was to replace the little stanless-steel washer at the rear end of the gas tube, where is exhausts into the bolt carrier. As you may not have a Swedish armourer's kit handy, the washer can be removed and welded up, the redrilled to a smaller size. You can then open it up, a thou or so at a time, until you have perfect functioning. Remember that these rifles were designed and fitted for Arctic-conditions usage. That's WHY they wing the brass so hard: they WILL function in 35 or 40 below. At migher temps, you don't need that much gas. Hakim gas adjustment CAN be fitted, the gas washer CAN be welded and redrilled, but the cheapest way it ro instal a set-screw, as pointed out many posts ago.
Stock disc gives you bore and groove measurements from the rifle's last inspection: bore diameter in millimetres plus wear over minimum, groove measurements as well.
SS stamped on a rifle's action does not mean the dear old Schutzstaffel. It means Sten Stenmo, the factory inspector, or so I am told (by the Swedes). If the Waffen-SS had any of these, they MIGHT have been stamped with the lightning-bolts. I am told they had a dozen or so, tried them out on the Ostfront. I REALLY want one!
You should be able to adjust any gas-operated rifle so that the brass just drops onto yur bench when you shoot. This is INVARIABLY the way to get the best accuracy...... and these things are scary accurate to start with..... likely the most accurate semi-auto battle rifle ever built.
Berdan brass (common out East from the seal-hunt) CAN be reworked to Boxer primers with a couple of little tools and a bit of sweat.
There WAS a special 10-round charger (stripper-clip, for those who don't understand the right word) for these rifles. MUCH faster than changing mags. There is also a dedicated BFA and sometimes you can find a set of self-luminescent night-sights, too!
But, DAMN, are they accurate!
Loud, too!
And fun!