I had got a Husqvarna Model 17 A in 1999 when all this informations were not available in the net as today. thought that this combination gun use 40 mm long brass cases like german rifles from this time

but I wonder about the long free bore you see here. the black line shows were the 40mm case ends and you see where rifling starts. it was ok for me because I load a .589 480 grains Lee minie bullet over 90 grains black powder with my .577 snider die set. the rifle dont shoot perfect because of the hollow base bullet but I get it in a 10 -15 cm circle around the target at 50 meter.

some years later I learned that Husqvarna chamber the combo's and rolling block rifles for a 50mm long brass case with a round ball

old Husqvarna catalog shows ammo for the Model 17 a 20/50 ( also in 24/50 and 28/50)
the Modell 17 B in 12,7x44R and the Modell 17 C in 9,3x57R 360

there was a thread once in the swedish firearms forum where such rolling blocks were topic. I think it was lost then in a crash years ago but I saved the pics from differnt rolling block bore rifles and ammo

slug the bore

old 50mm cartridges for the roller, different german made brass cases

new made 20/50 cartridges

12,7x44R and 20/50 side by side

maybe your rifle will do a little bit better with 50mm long brass