I use1/2" PEX plugs, from the plumbing store. They cost about $0.40 each, and slip right on the shaft. I also cut the head off a 3/8" bolt and chucked it in my redneck lathe (drill clamped in a vise) and spun it while filing down the threads until I could screw the PEX plug on snugly. Then I mount the plug and spin that while I file the edge sharp. When you are done, it looks kinda like a trumpet, with a flat leading surface and a sharp gouging edge all around.
Theswe work AMAZINGLY on rabbits and grouse.