Sounds like you just need to adjust the sights for elevation.

What sights does the rifle have, and how are they adjusted. Raising the rear sight will do the trick. If that's not feasible, fit a lower front sight.

Different brands of ammo may move the POI up or down a tad, and may also affect regulation to some extent. Welcome to the wonderful world of DR regulation!

You don't have a problem at all, merely a challenge!