Ljungmans can be really hard on brass.
So can SVTs.
So can ANY gas-op semi-auto; it is in the nature of the beast. Too much gas, or gas at too high pressure, and the actions work too hard and too fast and your brass gets battered.
The solution is simple. Make sure that gas gets to the action in the amount, and at the pressure, required for easy operation. ANY semi-auto rifle, including the FAL, the SVT, SAFN and the AG42B can get good groups with little-to-zero battering of the brass/ rifle action/ et cetera. Part of the REASON that the M-1 Garand is so accurate is that the gas to operate it is bled off very near the muzzle, at lower pressure, onto a big, wide piston; the action is very smooth and the gas impetus last for a very short period.
On the FAL, you adjust the gas bleed, which vents EXCESS gas. On the SAFN, you do the same; you just have to take off the front handguard to do it.
On the SVT, you use the factory adjustment tool to adjust the gas actually getting TO the mechanism.
On the AG42B the only possibility would be to load your ammo as perfectly as did the Swedes and then to load it to lower port pressures..... which would hamper your performance greatly. These things were made to function flawlessly in 40 and 50 below, which is WHY they batter brass at normal-human temperatures.
So you can't do ANYTHING for the AG42B......
EXCEPT (a) install a gas-regulator from a Hakim, then use it, or
(b) instal a set-screw into the gas-block on the rifle, or
(c) weld-up and re-drill to a smaller size the little hole in the small stainless-steel washer which the bolt-carrier telescopes over top of.
There is an earlier thread in this Forum on all three of these conversions. The cheapest one will cost under half a buck to do, given that you have any tools. That's cheaper than ONE fresh casing AND it makes the rifle even more accurate than it already is.... and they are very scary accurate just as they are.
And always remember: Thou Shalt Not Lubricate Thy Ammo. For many reasons, which my 2 fingers are too tired to type right now, this is really a SUPER bad idea: it puts ALL the pressure of firing onto the single bolt-lug. NOT healthy.
Take care.