I the Genesis I had I tried 150 grains with 295 Grain Powerbelts and it shot horribly. Also seemed like the bullet was tumbling. That combined with a lot more recoil than I wanted and the price, I cut back to 100 grains and the groups really tightened up.

That being said each gun is different and yours may not be the same way.

Mine shot 2 100 grain Pyrodex pellets and a 300 Grain Fusion bullet very well, as well as the 300 grain Speer Deep Curl bullets.

Heck, everything I shot in it shot great. It really shot great with the Powerbelts too, but unfortunately I had to ditch those due to the horrible performance I got when using them for deer.

I've got several big complaints about the quality of the Genesis that I had, but the accuracy wasn't one of them.