Went downstairs and excavated the data drawer. SAAMI MAP pressures for .38 Special are:

P: 17,600 cup/17,000 psi +P: 20,0000 cup/ 18,500 psi

Lead (swaged) bullet data is usually mild to minimize the chance of leading.

About powder company data, this is virtually always from specially made test barrels in universal receivers. The barrel creates an absolute worst case in terms of elevating pressures: tight bore and groove dimensions and minimum chambers & headspace. They'll generally hit max pressure for a given charge long before most production firearms. Then, there are the occasional surprises.