I finally found a Super Disc .45 cal. The tag on the gun said 1:20. The serial number was 005057 . I was under the impression that they switched the twist rate to 1:30 after serial number 005043. That would make this gun a 1:30 not a 1:20. When I check it with a patch and jag it does appear to be a 1:30 but I am hoping that I am not doing it right in checking the rifling. Does anyone know if the serial number change is correct? Would this gun be a 1:30?