For a homemade broadhead target this is what you do:
I got and old grain bag and then filled it with other old grain bags. After you have done this get wool from a sheep and put this behind the grain bags. Pack it very very tight, untill you cannot get any more in. Then sew up the top. I then makeanA-frame out of 1x1 wood to fit the bag and attach it with binder twinefrom hay bales. We used this target for broadheads out of my fathers crossbow and had good results. Although it does not last long (like a couple seasons)but it is cheap. I made it out of stuff I had around our farm. And we had sheep at the time so the wool was on hand. But I don't know where you guys would get that, unless you buy it.