Homemade Semiautomatic Airgun

Easy to build
Ever want a self loading airgun? I've built a very simple semiautomatic airgun that shoots any round ammuntion of the right size. At the heart of the system is my balanced spool valve. I'll do a detailed write up on it in the future, but for now, here's a video on it:

The valve works in a semiauto fashion when it is left attached to a air tank, whether that be a compressor, or the airpack I show elsewhere. To complete the system, a barrel and magazine needs to be added. I used 1/2" pvc for this. To attach to the valve, I first cut a piece of pvc about 3" long. Two lengthwise cuts are made about 3/16" apart and 5/8" deep on one side. I then cut the circumference, which leaves a piece of pvc hanging off with the before mentioned dimensions. This tab is to be bent downward, keeping the ammo from dropping into the valve.

I then selected a piece of 1/2" pvc about 15" long for the barrel. The same cuts are made on the breech end of the barrel that were made on the connection to the breech. This tab is left as is for now. They should look something like this:

Putting it Together
The breech connection piece is inserted into one side of a T fitting with the tab on the top side facing down. The breech end of the barrel goes in the other side, with the tab on the left. It will look something like this washed out picture:

Getting the Feed
I'm using some 1/2" marbles as ammuntion. I began by dropping one down the T fitting. It rolled down the top of the fitting and came to a rest. If the barrel is tilted downward or another marble dropped on top, it will roll out. To prevent this, the barrel tab is bent inward just enough to keep the marble slightly elevated and moved to the side.

The Magazine
Once the tabs are bent and the marble stays in place, I then added a few more marbles on top to be sure everything would stay in place:

Once I was satisfied everything was right, I used a marker to draw lines that would allow me to solvent weld it in the right position.

I cut another length of pipe to make the magazine. To one end, I added a 1/2" slip fit to 3/4" thread adaptor. A threaded cap prevents the ammo from being launched from the magazine. This is then solvent welded to the top of the T fitting to complete the barrel and feed mechanism. Here's the magazine and completed system waiting to be attached to the airgun:

Here's a video of it shooting: