After hours of tweaking the front derailleur, (toe in, toe out, up and down, screws loosened and tightened) shifting really sucks when going from the small ring to large. Just grinds against the large ring then goes over, no in between.

Could the chain or chainrings be a problem? Crankset is an old SR 48-34, chain is a new KMC Z33 NP Chain 5/6 Speed 1/2" x 3/32".

Shifting is fine from large to small ring and acceptable in the back 5 speed freewheel.

What do you mean by in between? That you aren't able to trim the fd?

Did it work before you changed the chain? Or is this a new bike/first setup?

It would probably help to state what fd you are using. Pics too if you can.

Firs thought is the derailleur is set too low. But that's just a wild guess. Follow due route's requests first

Back of on your pedal pressure when shifting. Derailleurs don't shift well under load. time your pedal pressure down stroke with the shift. Keep pedaling, back off on pedal pressure, shift, resume previous pedal pressure. In some instances, moving slowly, you need to speed up tick before backing off on pedal pressure for the shift.

This technique works wonders for both and rear shifting in both the up and down directions.