S&W issued a consumer safety alert on their M&P15-22. All rifles and pistols manufactured before February 1, 2019 could be affected.
The issue is that the rifle’s breech face counter bore depth could be out of specification, causing it to crush the rim on the .22 round, firing, cycling the bolt again, and causing multiple unintended discharges.
So far S&W has found two to be affected, but they’re cautioning all who have one of these rifles or pistols to cease use until after the bolts have been inspected.
There are two methods of inspection. You could do it yourself by ordering this tool, currently free of charge, or you could send the bolt in to Smith-Wesson for them to inspect.
Check out their video explaining in further depth what is happening and how to check to see if you have an affected bolt: