There's mention on another firearm forum about a conversation with
"James" of Wolf:

A rep named James stated with all .223 Wolf sells they will usually get a couple reports total per year regarding out of battery discharge for all brands of rifles. But this year they have had seven out of battery reports with the M&P 15. James said it includes both steel and brass cased ammo.

Posting links to items on sale Amazon and Office Depot gets "infractions" here, so you'll have to use your Google-fu.