PA Criminal defense lawyer here. u/muffpatty is correct and u/mehndeke is slightly off.

The max for an F1 is 20 years (or 10-20 under the min/max rule). 18 Pa. Section 1103

The max for murder 3 is 40 years (or 20-40 under the min-max rule). 18 Pa. Section 1102(d)

If you’re convicted of an F1 you could only be sentenced to more than 20 years if its stacked consecutively with something else. But murder is not an F1, it’s in a category of its own in PA.

ETA: there are also exceptions under the mandatory minimum sentences for 2nd and 3rd strikes for repeat violent convictions. Strike 3 has a 25 year mandatory minimum