Well, this isn’t a homemade airgun, but it is a homemade target that cost under $5 to build and is a blast to shoot:
The frame is made from 3/16″ steel rod. It stands 10″ tall and is 8.5″ wide. The corners were made by heating the rod to red hot and bending. The swinging targets are made from the same size rod, washers, and 1″ steel squares cut from an old lawnmower blade. The thick steel of the lawnmower blade should withstand many shots from .22 and smaller airguns.
Looking at the picture above, you can see how the swingers are put together. I didn’t bother cleaning up the welding other than wire brushing.
I finished it with a couple of coats of black paint. The targets get a shot of red paint to make them stand out. The 1″ square targets are perfect for keeping me in shape for small game hunting.
Here’s a video of the target in action: