I think you'll find they're fussy which mounts will fit so you may have to re use the mounts on your 4x40 if they fit well. i'd recommend a little simmons whitetail 1.5-5x20wa as they're a top heavy gun I found & a light little scope affects the balance a lot less. BTW a set of reach back mounts will suit your mercury better, look for a set of sportsmatch they fit well. I have a little simmonds 8 point 1,5-5x32 with these mounts spare if you are interested. Came off my merc .25 now sold so I know they fit well & give the correct eye relief without craning your neck foreward.