The Lyman 46th edition gives the following data for .38 Special 158-grain cast using 231 and standard primers:

Start: 3.5 grains, 675FPS, 9600CUP
Max: 4.9 grains, 906FPS, 16800CUP

+P: 5.2 grains, 956FPS, 18500CUP

Your stated goal of 3.8 to 4.0 grains should be a relatively mild load for a new shooter to learn with.