M-16A1 fire on safe

[Capt Nemo 882]

I ran into this when I was unit armorer in the Guard.

 

I had one M-16A1 begin firing while in safe. The weapon had just been certified, which checks trigger and hammer pin holes for wear. If these holes are worn, double firing may occur, as well as, firing when in safe mode. I then pulled the hammer pin and removed the hammer. The sear notch was full of hard black residue and the sear surface on the trigger was coated in the same. There was no metal to metal contact between the two. I then cleaned both parts and reassembled. I could no longer make the weapon fire while in safe mode. I checked the rest of the mechanism for play in the trigger and hammer. Everything was solid with no play. I got out the micrometer and checked the parts against specifications and everything was in tolerance even with very minor wear visible. After reassembly, the weapon was put through 10 function checks and passed every one.

 

This leads me to believe that the buildup of residue on the sear surfaces CAN cause this malfunction. I cannot see how this is possible with the way everything is built, but it still happened!

 

As the trigger components involved are identical on both AR-15 and M-16 series rifles, this should apply to both types.

 

Keep the sear notch on the hammer and the mating surface on the trigger as clean as possible, and do not allow a buildup of dirt to occur, as it may cause your rifle to malfunction.

 

Please spread the word!

[Sohei 10]

I have seen malfunctions with both worn and dirty trigger components in M16A2 rifles. It isn't always obvious just from looking at it in my experience. Many very dirty or worn components function fine.

[Capt Nemo 882]

I couldn't believe it either, due to the fit of the parts and everything being "in tolerance". It shouldn't happen, but it can!