First you need to correct the case sizing / expander problem you have ...
The XTP should Not spin freely in the case ... before or after it has been crimped .
Go back and read the manual again and see if they adress this ...
Usually a sizer sizes down the case enough ... Lee Carbide will even oversize at times ... but case tension should keep the XTP from spinning . Are you using dies designed to load Cast or Coated bullets ... these use an expander that runs larger than an expander designed for jacketed XTP's . Jacketed bullets should measure .357" , cast .358" - 359" .
Special larger expanders are used in die sets for Lead Bullet and are sold as Cowboy Dies .
Check what you got and let us know .
38 special dies will reload 357 magnum just fine ... my RCBS are 50 years old and it works ... Sounds like someone set your 38 spcl. die up to load cast bullets ... .358" and your jacketed bullets are on the slim side .3565" ... tolerances stacked to give you "Loose Fit" ... Die adjustment and/or larger bullet would have solved it ... but New Dies are Nice ...Load Safe
Gary

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