https://www.youtube.com/watch?v=a1z34TEmdnk
this is my adjustable core trimmer that i use to trim lead bullet cores for my 30cal bullets.. i was not overly enthusiastic about the garbage trimmers that Corbin and other companies sold, so i made my own.. being the core is totally enclosed in the trimmer, the core is supported on all sides and there is no chance of misalignment or variations in cutting length like the most commercial trimmers. i have not seen the need for a core swage die with this trimmer.. the bolt is the adjuster and the wingnut is used to jam the adjuster bolt. it is pretty precise. im about to make a better one with a finer adjustment and made of all steel with a sharper cutting arm that should do a lot better.