For a gun to be legal in the USPSA Production division, it must meet the general requirements:
2000 manufactured and available to the general public .
No magwell attachments or external flaring of the magwell, the lateral internal width of the well may not be more than 1/4" wider than the lateral width of the magazine. The lateral width of the well to mean the narrow width where the mainspring housing is inserted, the lateral width of the magazine to mean the narrow side that faces the mainspring housing when inserted into the handgun.
Meet additional requirements as set forth in Appendix D4 of the USPSA rule book