it sounds like a bad setup all around.
First, using the XTP, or any other JHP in a target load does nothing but add needless expense.
Even in a defensive loading, the 380 maintains a very tight energy budget that teeters between adequate penetration and terminal upset.
Your far ahead with a good flat nose design in this one.

Next is your powder measure.
the Hodgdon site shows min to max charges that spread over a half of a grain or less.
"whatever cavity works" is not a healthy thought process when developing a load.
You'd do better with something that you can infinitely adjust so as to better address the needs of any cartridge this small.

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it just needs more voltage