Here is another link
for you if you are feeling truly ambitious.
We really like the swingers we made in the pictures at the top but If you make your own follow this design:
1. The entire face should be either T1 or better steel and should be ONE piece. Cut it in the shape of a double ended lollipop. Ours were made of two discs welded to an angle iron beam. Even though we welded a bar to the back of the discs and the angle the disc still shot off due to some inferior welds with a 110 volt stick welder.
2. 1/2 inch thick will do. If you make it too thick then you will have to hit it multiple times in succession to get it to spin over. (This is what Gonehuntingagain was going for so our discs are about 3/4 thick.) Also make the disc diameters the same size. 9" is about as big as I would go.
3. Weld your axle tube (1/2 I.D. tubing) to the back of your one piece target face LESS THAN 1" above the balance point. You want it as close to the balance point as possible and still be out of balance enough to reset its self when it stops moving. Too far and it won't swing well. Make it as wide as the target metal so it is hidden behind the target but has a nice bearing surface.
4. Bend the target face in a slight curve around the axle tube by laying it on the floor tube side down and having a friend stand on one end and you apply weight to the other. Small bends make a big difference and heat at the balance point might help if the metal is hard. This will make the target hang more vertically instead of tilted forward. Check it after each SMALL adjustment.
7. Now weld some nice braces to the axle tube and the back of the target. This is the other part that broke from shooting on ours. 2 pointing up and 2 pointing down should do OK. Make them triangles that are about 4" x 4" x 3/4". 1/4" thick mild steel will be OK since they are protected by the target face.
6. Make your axle out of 1/2" diameter solid bar stock. 18" long ought to do nicely. If you want to get fancy you can drill a 1/8" hole for a cotter pin then put on a small washer then the axle tube then a washer and then drill for a small "quick pin". (you know, the ones that look like a heavy duty hair pin.)This will keep the target centered between the legs when the target spins.
7. make the legs as long as you want out of 1/2" square tubing. Weld a piece of strap across to make an "A" shape. then weld small pieces of the axle tube material on top at a slight angle so the legs kick out a little to the side for stability (and to keep them out of the line of fire). No need to fasten the axle to the legs, it wont go anywhere if the targets axle tube spins nicely.
9. SHOOT, SHOOT, SHOOT.