https://www.smith-wesson.com/mp15-22...r-safety-alert
There's a link to get a free inspection gauge towards the bottom of the page. Mine is on the way
Edit:
Here's the gauge link: https://store.smith-wesson.com/m-p-1...spection-gauge
I've about a gazillion rounds through mine so I'm not too concerned, but why not check it and get a free tool to boot.