Lots of Marlins made over the years shoot either high or low with factory sights. Most of the time it requires a different height on the front sight, like others have said. Back when the 336 in 35 Remington came out, I had an uncle who bought one and it shot way low. He put a scope on it (an old Weaver K4 with a post) and used it for decades. I had a 25-20 1894 CL that shot so far off that I ended up putting a ramp on it just to get a sight that would be high enough. Like a fool, I didn't send that rifle back for a new barrel. It shot OK but I ended up swapping it for something else.