the rolling block would be a wonder in .357 maximum with ability to fire other sizes. I'm sold.
Can't imagine that 500 rounds through it with soft lead target .38 would be a good idea at all. A box once in a while for the 10 year old boy probably wouldn't hurt. But it also begs the question of whether the round would even work.
So the point is completely wasted thought, if a person handloads, I guess. Just download the brass that you have.
It might be a good idea to bottleneck maximum brass to only fit the bullet so that the low pressure .38 equiivalents don't have to expand the whole length of the brass. I dunno.