Case Trimming

[Joe King]

I did a large scale experiment on trimming with a handful of dies and a handful of rifles.
Each population of brass was kept to one die.
I measured the case growth and trimmed with an RCBS 3 way in the vertical mill.

The lessons I learned are close to common knowledge.
The best way to trim is to not trim.
The best way to not trim is to keep brass dedicated to one rifle and either neck size, partial fl size, or push the shoulder back .001" with a FL die.

I could do 25 firings of 223 at 66kpsi by using a Lee Collet die, without trimming.

There's nothing 'wrong' about doing that but normal variations of the necks in individual case will have a much bigger effect on grip than a few thou of length.

This pretty well sums it up for me.

 

[jtkratzer]

I don't have a ton of experience, but why would you not trim? Seems it would keep consistency, especially for loads with a crimp.

 

[Mikecr]

I don't see any implications that trimming shouldn't be done, at least early in preps/forming.
But it would be a real pain(to re-trim & re-chamfer well), and sometimes unnecessary to do frequently.
It's an indicator of brass changing, as it's being trimmed away, and I for one prefer that my brass does not change at all.
I also do not like huge clearances from chamber end, as this contributes to excess sooting and higher ES. So I would not trim brass to some unknown, or inappropriate value for MY chamber.

If you have to do a lot of FL sizing, you're gonna have trim more frequently, so you might as well set up a good process for it. All we do IS a choice,, one leading to others.