Are you using the BDC reticle scope or are you just familiar enough with your equipment that you know where to hold at certain distances? When I bought mine I believe it was designed for the Omega or a lower grade model than the Encore. I still use it on my Encore and it has worked flawlessly. They may have since come out with a newer version that is just for the Encore or multiple models. Anyways this is the scope I use on mine and its absolutley dead on out to 200yds. I use the BDC and shoot 150gr in mine as well but I am honestly not sure if the scope works the sameway for 100gr, Maybe it makes no difference to the amount of powder as long as you sight it in according to the directions. I do know that you have reticles for in between yardages and this may help you out with your problem. That would be my suggestion if your not already shooting one but again Im not sure if you have to shoot 150gr with it or not. Not a whole lot of info I know but if your not using that scope I would definitely give it a try. Good luck and let us know later on if you get things straightened out.