I've de-capped live primers also tho' not over a half dozen or so. Primer Mfgs always warn about getting primers contaminated w/ oil or grease as causing them to be inert. Stands to reason a drop or two of oil in the case would render the primer inert. ( let it soak in for a min. or two) After de-priming blow the case out w/ brake cleaner. You for sure want to wear safety googles for both steps ;D I've never put oil in cases but, if you're concerned about safety this might work for you.