hello

12,7x44R is easy
the 20 ga, we had it before and what I know the husqvarna bore rifles use a 46mm long case with a roundball and BLACKPOWDER ONLY

http://forums.nitroexpress.com/showflat....;gonew=1#UNREAD

the gun is build very strong but I suggest only blackpowder! have a Mod. 17 a in 20ga /28 ga rifled
and I load 90 grains PP under a 480 grains Minie bullet which I slug to the .600 groove diameter.
never feels its to much for the action but better work with a roundball or maybe a custum made paradox style bullet.