I got a new Fender Mexican Strat Saturday and bought some 9-42 supper bullets. I just put the new strings on and it seems like it's badly out of tune even though my tuner says it's fine. Also when I hold down some of the lower frets the strings will rattle against the frets. This happens even worse when I palm mute. Help?
It could be the intonation that's off. Adjust the truss rod or take the guitar to a shop that can do it. The fret buzz might be because the action is too low - adjust that too.
sounds like the strat came with heavier strings stock so now the neck has less tension and is bending, thus causing the buzz. You just need a neck adjustment, and possibly a saddle adjustment to go with that(which would explain your intonation problems).