What weight bullet were you using? I'm also assuming that you actually have a Model 15-2, not a Model 15. The Model 15 has a pork chop barrel shroud so they're easy to differentiate.
DW makes two sight blade heights for the Model 15-2. One is .250" and the other is .300". If you have the .250" front sight blade and are using ammo with 110 grain bullets then you can expect the point of impact to be pretty high. Most model 15-2's are regulated for 158 grain bullets using the .300" sight blade and for 125 grain bullets using the .250" sight blade. Both these sight blades can be found with white, yellow, red, or orange inserts so you can't use the color as an indicator of height.
It's not real common but I have run into Model 15-2's that have a model 14 barrel & shroud on them (and vice versa). The Model 14-2 uses a fixed rear sight that is lower than the adjustable sights on the Model 15. It takes a .200" front sight blade. The Model 14-2's front sights typically have no colored insert.
I once had a Model 14-2 that had a .300" Model 15 front sight blade on it. It shot about 10" low at 25 yards (just the opposite of your problem). Once I installed the correct .200" front sight it shot to point of aim.
Check your front sight height. If it's .300" high then try using some ammo with 158 grain bullets. Likewise, if you have a .250" front sight then it ought to shoot 2-3 inches high with 158 grainers. DW still sells front sight blades for the Model 15-2. They're somewhere around $15 if I recall correctly.
On the other hand, if you actually have a Model 15 with the pork chop shroud then a Model 15-2 front sight can be made to fit, but it does require some modification to work.
-Lee
