You'll need at least medium rings depending on the base or bases you use with a 50mm objective scope. I need medium rings (I prefer Leupy STD rings/bases on all my hunting rifles because the external windage adjustment for the rear ring allows me to set up for sighting in at mechanical zero for windage. You'll need to match the ring style to the base style to get it all to work.) for my 44mm objectives. I'm currently acquiring a 50mm objective scope so I'll have to measure.
If in doubt, contact NF customer service or a good gunsmith...they'll be able to help you.
Hope this helps,
FH