Originally Posted by alwslate

You can experiment all you want, nobody's stopping you and
if your gun has the same metalurgy as a 357 then you might
be able to push pressures to 357 levels without blowing up
your gun. But you are still working with less case capacity so
357 velocities cannot be achieved at 357 pressures. But in
such experimenting you bear full responsibility for the
outcome. Expecting manual publishers and powder companys
to provide load data for such ventures is ludicrous. Published
data will vary between sources but will generally conform to
industry standards. I have older manuals dating back to the
60s and I don't see the "much higher" listed loads you refer
to. I have seen a few published loads that were fairly warm
with a notation that the loads were already used extensively
by handloaders. Like minded experimenters on the good old
net might be your best source for data.