Have you ever wondered if there is a right or wrong way to install your Hammer and Trigger pins? It turns out there really isn't a wrong way but there is a way that is slightly better and easier for you during building your lower.
If you look at the pins, you will notice that there is a small notch in the middle of the pin and another one roughly halfway from the middle to the end but only on one side. The hammer pin will utilize the center notch and the trigger pin will utilize the one closer to the end.
The center notch will engage the tiny spring that you can see when looking through the pinhole on your hammer. The side notch is where the (external) hammer spring locks into the trigger pin to help it stay in position. For this reason it is important that you install your trigger before you install your Hammer when completing your lower. Mind you it would be quite difficult to install the hammer first and then the trigger but we have seen some crazy things come across our workbench.
If your Lower receiver suffers from walking pin syndrome, it would be a good place to start by looking at your Hammer, Hammer spring, Trigger pin and Hammer pin. If the undercuts in the hammer and Trigger pins are worn out for some reason the pins will be free to walk. If the hammer spring is not properly engaged in the trigger pin the trigger pin will walk and if the 'J' spring built into your Hammer is worn out or broken your Hammer pin may walk.
Sometimes simply installing anti-walk pins is a cost-effective solution to these problems, however that should be reserved for situations where the hammer and/or trigger pin hole in the lower receiver has worn for some reason which might also result in Walking pins in specific situations.
When it comes to building your Lower, your trigger pin can be installed however you like with no real concern for the orientation. However you can do yourself a favor when installing your Hammer pin by ensuring that the pin end with the off-center notch does not go in first. Doing this, the 'J' spring inside the hammer does not get stuck in that notch in the trigger pin as it passes through the hammer. This will make your life a little easier and will work the J pin inside the hammer a little less which will hopefully help your lower build to last for many years.
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