I can get a real good deal on a 1.4 x 4.5 Nikon scope it is new and called the Monarch turkey pro. it has the crosshairs with a circle in the middle. I would be putting it on my Knight Extreme Rifle. would this work ok ? It says it has a parallax setting of 50 yds, I dont know what that means but will it stillwork on my 50 cal. Thanks for the help !!