I have a Diana 350 N-tec. that likes to shoot low even with open sights, the gun is extremely accurate otherwise. I checked the barrel and it looks straight to me. I put washers to raise the back sight so the spring of the open sight stays tight. It's already heavy and I shoot freehand so I don't want to scope it but I also don't like the way it looks with the washers. I'm very reluctant to bend the barrel because I don't want to risk losing its perfect grouping. Is there any other way to keep the iron sight tight without these fixes?