You need to slug your chambers and barrel to determine the proper diameter cast bullets to use. You are just hit and miss otherwise.
Cast bullets MUST fit the chamber mouths snugly and be at least the same diameter of the groove diameter of the barrel or larger.
Generic sizing sometimes works and sometimes doesn't for an accurate cast bullet. Better to determine the diameter that your particular gun needs from the start.
Also many gas checked bullets will have the check run as much as .001 larger than the bullet sizing due to "spring-back" of the check after sizing.
Regards
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