Should have found this forum first, but I didn't. Anyway, I have a Bushmaster 9 mm Carbon 15 flattop. I also have a Barsika 4x28 IR Electro Sight. I bought the sight assuming that it would slide onto the rail and sit above the fixed front sight of the rifle, but it does not. As it is now, the telescopic sight looks directly into the fixed front sight. Can I just buy a riser, mount that onto the rail and then mount the scope onto that riser to get the scope above the sight? Do risers come in specific heights that I need to know in order to get the right one? Should I buy a particular manufacturer of riser to make this Barsika sight fit on the rifle?