AR-15 Build Part 6

In B.O. Special, I introduced the newest addition to the gun cabinet and reviewed the rifle kit from Del-ton.
In Part 1, we talked about tools and preparation and installed the magazine catch.
In Part 2. we installed the trigger guard.
In Part 3, we installed the bolt catch.
In Part 4, we installed the pivot pin.
In Part 5, we installed the trigger assembly.

This time, we’re going to install the hammer.

There is a pin called the “J-pin” that goes into the bottom of the hammer and pokes up into the mounting hole. This pin is what locks into the center groove in the hammer pin in order to secure the pin and keep the hammer centered.

This pin was already installed in my hammer so I don’t have pictures or instructions for installing it, but if is not installed, it will need to be so before anything else.

Assuming that the J-pin is already installed, the first step, as with the trigger, is to install the spring. The spring is very similar to the trigger spring and goes on in much the same way (and is just as hard to describe).

The spring goes onto the hammer from the rear, with the coils facing away from the hammer, the closed squared loop up and the open legs pointing down.

As with the trigger spring, the coils go over the protrusions on either side of the hammer through which the hammer pin hole passes.

When properly installed, the closed end should be resting against the back of the hammer and the legs should be pointing down and forward.

In order to install the hammer assembly into the receiver, you have to tip it forward and place the ends of the legs on top of the trigger pin.

Then rotate it to the rear and press it forward and down against the spring tension to line it up with the mounting holes in the receiver.

Again, I used a pin punch to line it all up before installing the pin.

Be sure to insert the end of the hammer pin without the off-center groove first. In other words, if the pin is going in from the left as pictured, the off center groove should be to the left.

If you put it in the other way, the off center groove will enter the hammer first and the J-pin will lock into it…which will complicate things.

As the pin is pushing in, the punch will be pushed out the opposite side. You may have to jiggle the hammer a little to get the holes aligned and there may be some resistance as the pin pushes past J-pin in the hammer. You will feel the J-Pin lock into the groove in the hammer pin as it centers.

In this picture, you can also see the hammer spring legs clearly atop the trigger pin. The leg on the left side should seat into the groove in the trigger pin locking it into place.

Installed with the hammer cocked.

And, from the side with the hammer decocked.

Don’t dry fire the lower receiver without the upper installed. The hammer will impact the aluminum receiver and the bolt catch and may damage either or both.

That’s all there is to it.

We’re almost done. Next time we’ll install the selector switch and pistol grip.

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