Re: bullet comparator question
As mentioned, most people use bullet comparators to measure the distance from the base of the case head to the bullet ogive on loaded rounds so you can seat the bullet off of or in to the lands some specific amount.
You can also use a bullet comparator to measure from the base of the bullet to the ogive, or if you have two comparators, the actual bearing surface of the bullet. Most people I know that sort like this use the biggest pile for matches or other serious use, and the rest for practice. They aren't necessarily 'junk' in any meaningful terms, you just hope the gun shoots a little better if you keep them segregated - I don't know that I've seen any one claim that their gun shot great with the bullets that measured 0.002" longer than the ones that measured 0.002" shorter out of the same box. The group size may (or may not) go down compared to *unsorted*, but thats about it.
In all honesty, if this is your first go-around with a bullet comparator (sounds like it) you might be better off not worrying about sorting the bullets and just getting a handle on your seating depth (the first use I mentioned) for a couple years. Then, if you still really think the only thing between you and the accolades of your peers
is sorting the bullets like that... well, some people say there are better tools for the job than a run-of-the-mill bullet comparator. That is, of course, assuming you aren't talking about a dedicated bullet sorting comparator like the ones sold by
Tubb, Hoover, Buhay, Greene, etc.
YMMV,
Monte