I have two Nikon Monarch 3x9s and love them. They sit atop of a Ruger No 1 in 45-70 Gov't and a Savage 110 in 7mm Rem Mag. They are great scopes, clear, pull in a ton of light and hold zero well.
I think you would be very happy with the Nikon. My only suggestion is 50mm is a pretty big objective. It will likely require a tall set of rings to mount it correctly on your rifle. Just keep that in mind.
Also, what distance do you plan on shooting? If it is under 300 yards or so, a 3x9 might work just as well for you. I had a Bushnell 6x18 and even out in Wyoming hunting antelope I never went above 9 power. Here in the woods of Kentucky 4 power is about as far as I go.
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