i have the same problem with my guide gun in 45-70 but with the factory sights, it shot about 3 feet low at 25,50,and 100 yards.
i read somewhere that marlin let a few 1895s get out the door with the wrong sights on them so i called them up and expained the problem and they kindly admited to this and have sent me the proper sights for my gun.. as of now they are in the mail..i called them on feb.7. i will post how it shoots when i get them here and let everyone know the results..
i want to tell you that i bought this gun used and it had only been shot 2 or 5 times prior to me getting it, i even told marlin that, and it was no problem.. my first experince with there service dept. and i have to say they are top notch !!