If your hammer and bolt are getting beat up from where your hammer is contacting the bolt below  the firing pin your hammer is too short. Most after market hammers are too short. Most AR 9mm bolts seem to use a colt style firing pin. What happens is a short hammer comes to rest on bottom of the bolt rather that the top of the bolt where is designed to rest. This causes early firing pin failure and other problems.

The way it is suppose to work is that the firing pin protrudes out past the end of the bolt, a little, held there by the firing pin spring. As the hammer comes up it hits the firing pin first, then the hammer should hit top of the bolt above the firing and stop. The firing pin then continues on its way without the hammer delivers its kinetic energy to the primer. The firing is also allowed to rebound back to below the breach face.  

When hammer is too short its contact time with firing pin is too long. The hammer travels beyond the rear of the bolt coming to rest on bolt hammer relief cut into the bottom of the bolt.  This extended contact time with firing also is not delivered perpendicular, thus it is bending the firing pin a little.

Next during bolt recoil instead of the top of the hammer be driven to the rear by the top of the bolt, the very small surface of the bottom of the bolt blow the firing pin is the contact point with the hammer. The hammer is also dragging across the firing pin. The speed of a unlocked bolt, the low mass of bolt and buffer makes the impact violent, thus destroyed triggers. Also because the mass and its distant from the rotation point on after market triggers is less than the stock trigger this aggravates the problem. Most after market triggers reduce there mass and move it closer to the pivot point to decrease lock time.

So triggers with factory length hammers only, only one I've seen Jard adjustable.

Interesting.........I've used a few different triggers in three 9mm builds. Must have fired at least a total of 6-7k rounds.
I've never had a damaged hammer or a broken firing pin

Lucky?

If you go back a few days on the front page, , you'll see my AR trigger thread with a list of what works and doesn't work.


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