Just thought I'd follow up. Started with 4.0 gr with both 125 gr cast bullets and 125 gr FMJ bullets, Fiochi Standard small pistol primers, and CCI mag primers. No noticeable difference in any of these loads. Most barely ejected, a few did not eject fully. Retried these same combos with 4.5 gr, gun functioned flawlessly, and all rounds appeared on the paper target in the same relatively tight group.
Why try mag primers? Because I have a lot of them and wanted to pretest in case I run out of standard ones.