Umarex Hammer - 550 slug

I recently purchased the Hammer and have been sighting it in using the 550 grain slug. I have very good accuracy at 25 and 50 yards, however at 75 and 100 yards there is significant drop with the 550 slug. Anyone else using the 550 slug? For longer distances should I go to a 350 slug?

Ballistics! Try reaching further and see where the effective range stops.