Hi, I've had two. Got rid of my first then replaced it because I missed it Yes, the fixed sights are off. Both off mine were high and left by 3" I improved the gun no end by putting an under barrel laser on it - great fun and miles more accurate.
If it's grouping well try another pellet? Might just group in a slightly different spot? Worth a go anyway. I'm using Crosman Accupel with good results. Some pellets can cause problems with mag indexing though.
Hope this helps
Binker
Worth mentioning that I usually use mine at about 6-8m which might account for the extra margin you're experiencing. It is a blowback after all