What gun is this? You may be able to get new sights if it is a Marlin. Get a dial caliper and call customer service so you can explain the issue and give them the dimensions of your sights. They may be able to figure out just how much taller your front sight should be.

Other than that, I guess you'd need to alter your sight picture. The six O'clock hold may work. If the gun has been owned and used successfully by others, I'm thinking the issue may be with the way you are using the sights. Hard to say though.