SIG found the problem that exists for .300 BLK version, but is extending the recall to all MCX with serial number range from 63C000044 and 63C003702. If the serial number ends in 25000 or higher, you are ok
To get the problem fixed, contact SIG Sauer at 603-610-3000, and press for option 1
https://www.sigsauer.com/press-releases/mcx-mandatory-carriage-assembly-replacement-program
The recall will replace the Carriage Assembly to the Gen 2 version
From: Sig Sauer