I have made one using O-1 drill rod from advice I received here. Cut a bit off and chucked it into a drill. Place the drill in a vice horizontally. Used a couple of files and a caliper to keep tabs on my progress. Took little time. Not much more than half an hour. Only caveat is it heated up a bit and I measured as I went. When it cooled it had a bit smaller diameter. Still worked fine in the gun. I would suggest a wet rag to cool it before taking measurements as you go.

I had a 28g. gun I had trouble shooting due to a pretty large front bead. Dewey helped me with it at his house since it fit me but I could not shoot it well. He took the large front bead off, we went into the basement and he chucked it into a drill set vertically in his vice. He then proceeded to reshape it using files and sandpaper. Took a few minutes, reinstalled and problem solved.