The Firing Line Forums - View Single Post - M4/M16 full auto trigger , How does it work

marine6680 · February 27, 2015, 06:28 PM

Full auto has an auto sear, that holds onto an extra hook on the hammer... when the bolt is fully into battery, the auto sear is tripped to release the hammer...

Think back to AR profile bolt carriers, and M16 (full auto) profile bolt carriers.

The AR carrier has less material at the lower rear section... This is because that area on a full auto carrier is what allows the auto sear to work.

The auto sear sits at the rear of the lower receiver, and when the carrier moves forward to the point that the bolt is closed; the lower portion of the carrier comes into contact with the auto sear, and trips it to let the hammer fall.

If you let go of the trigger, the auto sear is still tripped, but the semi auto sear is in place to catch the hammer after it falls a very small amount when the auto sear catches it.

I actually find the burst trigger more interesting, as it is more complex.

February 27, 2015, 06:28 PM	#5
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	Full auto has an auto sear, that holds onto an extra hook on the hammer... when the bolt is fully into battery, the auto sear is tripped to release the hammer... Think back to AR profile bolt carriers, and M16 (full auto) profile bolt carriers. The AR carrier has less material at the lower rear section... This is because that area on a full auto carrier is what allows the auto sear to work. The auto sear sits at the rear of the lower receiver, and when the carrier moves forward to the point that the bolt is closed; the lower portion of the carrier comes into contact with the auto sear, and trips it to let the hammer fall. If you let go of the trigger, the auto sear is still tripped, but the semi auto sear is in place to catch the hammer after it falls a very small amount when the auto sear catches it. I actually find the burst trigger more interesting, as it is more complex.