Bigmon... I think there is a tutorial here for it, but it has been a long time since I have seen it. But it is really quite simple... All you are doing is hammering on the edge of a piece of metal, held in a vise, to 'mushroom' it into a trigger. This is how I make all of my triggers now. I used to hot forge them, but this cold forging method makes that rather silly. I use a ball peen hammer, and start slowly. Once the mushroom form is started, it is easier to judge the blows. It is actually quite satisfying once you get into it.