.353 is about right for jacketed bullets. That gives .002 bullet tension grip on .355 bullets.
+1^^^^^^^^
Most reloads don't understand what a expander is, what the dimensions should be for the size diameter bullet their trying to reload. Let alone what the flare should be compared to the amount expanded for consistent neck tension.
A link to a company that makes/sells custom expanders.
Expander Plug (Pistol) | NOE Bullet Moulds
They give you 2 sets of numbers. The 1st number is the amount of flare. The 2nd number is the amount of expansion the expander body will do.
They also sell powder thru expanders that have 2 sets of numbers also.
Pistol - Powder Through Expanders | NOE Bullet Moulds
most factory expanders are designed for jacketed bullets