The M-16 and AR families have a design feature that keeps the gun from being able to fire out of battery.
The firing pin can not stick through the boltface until the lugs are rotated into lock with the barrel extension.
The ejector is also part of this safety in that the ejector keeps the cartridge pushed away from the boltface until the cartridge has stopped in the chamber against the chamber shoulder and the bolt/career compress the ejector enough for the bolt lugs to rotate into lockup.
Once you understand how this works, you can see that’s it’s nearly impossible to get an out-of-battery detonation from the firing pin striking the primer before lockup. If you get an out of battery detonation in an AR type firearm, it’s likely from foreign debris or perhaps a piece of the firing pin that broke off and is caught in the boltface but it won’t be from a firing pin in serviceable condition.
