I saw a really neat video once. I think it was on the crtical past sight or one of those archive pages like that. But it had a vintage video of them straightening barrels at SA. The funny thing to me at the time, they did everything by "eyeing" it. I guess I just never thought of it, and to see it done in such a simple process, it really amazed me.

If I could remember where I saw it, I would post a link. It was sort of neat to watch.