"1. What do you use as your "rule of thumb" for when to trim?"
Book max case length.
"2. How do you determine your MAX length before you MUST trim?"
Same book, same length.
"3. What is the end result if you fail to trim when you "MUST"?"
I get nervous. May be safe but being wrong would be disasterous.
Okay, I actually have Sinclair type chamber length plugs to find the front edge of my chambers. Most chambers are longer by some 15 to 40 thou but it's by no means consistant,. I know one guy who has a chamber only a couple thou longer than max book case length! There is NO advantage to allowing cases to grow longer than normal SAAMI max length so I don't allow it.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tribe</div><div class="ubbcode-body">1. What do you use as your "rule of thumb" for when to trim?
2. How do you determine your MAX length before you MUST trim?
3. What is the end result if you fail to trim when you "MUST"? </div></div>
I run the brass through the trimmer every reload cycle. Takes less then 3 seconds per round with the lathe, no reason not to.
If you do not trim and the case gets signiicantly out of spec, it can get long enough that when fired, the end of the neck runs into the end of the throat in the chamber. And having no where else to go, it will turn inwards and grip the bullet like nobodies business. This leads to massive pressure build up and "bad thngs can happen".
It will tell you what your trim length is for your rifle, once you have that number you'll know exactly what length to set your trimmer up for, I use a Wilson, my .308 trim length is 2.016, I set my trimmer to that length, I put every case through it, some don't need trimmed some do.