PLEASE DO NOT POST UNTIL IT IS FINISHED. YOU SHOULD BE ABLE TO TELL IF IT IS OR NOT.
Here are all the materials you will need

10" of 1/2" PVC
12" of 17/32" brass
4" of 9/16" brass
2 1/2" stubs of 19/32" brass
E-tape
Before we can start making anything we have to prepare all the tubes.
First take your 17/32" tube and grind out the inside of one end with a stone grinding bit.

Now take your 4 inches of 9/16" and flare out one end with a pair of needle-nosed pliers.

Then take your PVC and sand down one end as shown. This end will be the base of your barrel, or the end which goes into the coupler.

Now that that's finished we can start contructing the breech. Start by marking 1" from the base of the PVC.

Now make a half-pipe outline on the PVC. You can make the cut however long you want, but it shouldn't be much longer than your darts. I make a cut about 2 3/4" long, because I know I'm not going to be using stock darts.

Cut it out and then pop it out with a screwdriver.

Now take your 9/16" brass and line it up with the PVC and mark where the end of the opening is.

Then make another outline on the brass.


Now cut out the outline. I used this wafer-like disc, and it worked well:

Once you cut it out, and line it up against the PVC and make sure the cuts are similar in length. Also make sure that the 17/32" barrel slides in and out of it with relative ease. If it doesn't try sanding out the cuts or try to locate the point of friction. I personally had no problems with this.

Now wrap e-tape around the top most rim of the 9/16" and the bottom, and make sure that they have a nice snug fit in the PVC.

But before you glue it into the PVC, put the 17/32" barrel down and mark where it ends.

Wrap e-tape above that line to make a snug fit, but not so tight that it makes it hard to move it around in the PVC.
Now super-glue the 9/16" piece into the PVC. I put some e-tape on the bottom so that the glue had something more to stick to.

Make sure that the cuts on the brass and the PVC line up (this is completely necessary, but for aesthetics).

Now put your 17/32" barrel down the PVC and into the 9/16" brass. Pull the barrel out until the end of it meets the end of the hole in the 9/16" brass. Now mark on the barrel (17/32" brass) the point where the PVC ends at the top of the breech.


Now go grab your 19/32" stubs. Line them up on the 17/32" barrel, toward the base of it and mark where the last one meets. It's hard to explain this in words so here's a picture.

Now put some etape on the brass where the 19/32" stub will be, and then superglue it on.
