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Posted: 10/22/2014 8:47:21 PM EDT
| We were shooting my buddies Spike's AR today when the hammer would not drop when he pulled the trigger. I opened it up and noticed the hammer looked cocked to one side. Then I noticed the drift pin that holds the hammer assembly to the lower had walked out a third of the way, and was no longer in the hole on the right side of the lower. I was able to push it back into place with just finger pressure, it was not snug at all. Any solution? Do they make slightly oversized pins that can replace the ones that are loose? |
| The hammer has a pin in it called the "J" pin. It engages a groove in the center of the hammer pin. It sounds like it may have broken or fallen out. If you remove the hammer, look at the bottom of it and you can see this J pin. There is also a hole in the side of the hammer where it is visible. It is just a little wire looking pin. |
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Quoted:
check that the hammer spring is installed correctly if its not the pins can walk but when installed the right way they will not http://i707.photobucket.com/albums/ww75/Isaac_Glass/Tag/AR15-HammerSpringInstall.jpg Hammer spring shouldn't affect the hammer pin, it retains the trigger pin though. This is the "J spring" that's in the lower part of the trigger and snaps into the groove in the middle of the pin. 
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| Hmmm. I thought that the hammer pin being installed incorrectly as noted in the above picture results in less "upward" pressure on the hammer pin, thus making it more likely to walk. I understand the J pin is primarily holding it in, but I thought the correct installation of the hammer spring also helped. To me, it's sure a heck of a lot harder to install the hammer pin (in terms of getting everything lined up) when the spring is oriented correctly than when it's not. I'm not saying you are wrong by any means, I'm just saying what I thought, and maybe I'm wrong on that. |
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J spring gets installed into the hammer via the bottom channel, then the J spring is peened through the side of the hammer openings holes to hold the spring in place.
The quick way to peen the spring, punch up through the bottom hole against the spring/back the bottom punch on a hard surface, then a punch down through the top to strike that J spring to peen the top of the spring. flip the hammer over, then peen the other side of the J spring through the hammer hole again on the other side. Look close at the spring through the side holes in the hammer, and you can see the J spring has been peened to hold it in place. 
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