If you own one of these rifles manufactured before 1-Feb-2019 you will want to check this out. https://www.smith-wesson.com/mp15-22-consumer-safety-alert
Smith and Wesson will send you a bolt inspection gauge for free here https://store.smith-wesson.com/m-p-15-22-bolt-inspection-gauge
Smith and Wesson will send you a bolt inspection gauge for free here https://store.smith-wesson.com/m-p-15-22-bolt-inspection-gauge