FC changes the output format to
FeynCalcForm. To change to InputForm use
FI.
Overview, FeynCalcForm, FI, FeynCalcExternal, FeynCalcInternal.
FI
{DiracGamma[5], DiracGamma[Momentum[p]]}{DiracGamma[5], DiracGamma[Momentum[p]]}FC
{DiracGamma[5], DiracGamma[Momentum[p]]}\left\{\bar{\gamma }^5,\bar{\gamma }\cdot \overline{p}\right\}