For one, pellets are a big waste of money IMO. I don't think it's really more convenient to get pellets out rather than pouring some powder into a measure. Also, powerbelts aren't very tough bullets. They're going to perform best at lower velocities. Pushing them too fast is when guys have problems with 'shattering' their bullets. I use 130gr charges, and I shoot 250gr shockwaves without problems. It also sounds like you aren't planning on shooting very far. Not really a need to shoot more than 100gr when you're only shooting to 100yds.