AR15 and  M16 firing pins do have different diameter collars, the M16 being larger.  Notched hammers do not mix well with M16 firing pins.  This is not an issue with most of  the current upgraded AR15 carriers with the shrouded firing pin.

My solution years ago was to use M16 hammers with the hooks removed in all the semi-autos I built along with M16 Carriers.  No more woes.  The manufactuers came along and saved me some work by providing non-notched semi auto hammers and now shrouded firing pins on the improved AR15 carriers.

All the crap, ie notched hammers and non-shrouded firing pins were all attempts to make illegal conversions more difficult, but also adversely affected reliability in some rifles.  The larger diameter of the collar on the M16 firing pin can hang on the notch in the notched hammer  with an unshrouded carrier.

The cheapest solution is to switch to an AR firing pin, but this is not always a 100% solution in all rifle due to manufacturing variances.  The next cheapest solution is an AR15 firing pin and a non-notched or modified M16 hammer.  The 100% solution is a non-notched hammer, AR15 firing pin and a current shrouded bolt carrier.

Denny

There you go. See. A simple solution for under $20. No more problem.



JohnM at Home