trim to length accuracy

[std7mag]

Does it make a difference on target? The few i have that need trimming i let grow to .010 short of chamber and measure and that is my trim length. My AI cases have never needed a trim.

Oh, they will need trimmed.
Just because the shoulder is at 40° doesn't mean that it won't elongate.
Brass has to flow somewhere. Path of least resistance is at the neck.

I trim my brass every reload with the Lee case length gauges.
While I'm not trimming as much brass off my AI's, it still takes some each time.

 

[Seabeeken]

Oh, they will need trimmed.
Just because the shoulder is at 40° doesn't mean that it won't elongate.
Brass has to flow somewhere. Path of least resistance is at the neck.

I trim my brass every reload with the Lee case length gauges.
While I'm not trimming as much brass off my AI's, it still takes some each time.

I am still shooting Jamison brass in my 257ai that has 10 reloads on it and 9 years old and never been trimmed.
7x57 brass with 12 reloads on it 8 years old never been trimmed. Had to replace a few due to primer pocket wearing out.
250ai with 12 reloads on them, never trimmed but did just find some donuts.
Just recently started load development in 244ai which had to go in trimmer but not for length, just to square up mouth since one side stretched more than the other during fire forming. They now have 5 reloads on them and not close to needing trimming.
Same for my 280ai, 243ai and 284.
All get bumped .001-.0015
6xc, 22xc, and many others that haven't needed trim yet. My trimmer is the loneliest thing in my reload shop.
Although I seldom shoot them, my 308, 243, 22-250's would get trimming now and then. I trim more 223 than all else combined

 

[Mikecr]

Oh, they will need trimmed.
Just because the shoulder is at 40° doesn't mean that it won't elongate.
Brass has to flow somewhere. Path of least resistance is at the neck.

Not necessarily.
Brass 'flow' is actually just yielding to fill in clearance gaps (on firing), and rolling of brass up cases (with die sizing).
You can reduce clearances and excess sizing to a point where there is no growth with reload cycles.

 

[Varmint Hunter]

Load up a few of the longest cases and a few of the shortest cases. Fire them for group and POI. I'm willing to bet that you cannot see the difference.

I prefer to leave my brass long, providing that they aren't so long that they present a problem with the chamber end or the carbon ring, which is always present to one extent or another, I never cut cases to the minimum length indicated in the reloading manuals.

 

[marchboom]

I hate to somewhat change the focus, but what case trimmers will hold a tight tolerance for less than $200? I have an old original RCBS rotary trimmer and struggle with consistency. I think it has to do with tightening the case in the collet and the collet moving away from the cutter as you tighten it. Looking to get better consistency without breaking the bank.

That's the same problem I had. Get the shell plate conversion from RCBS. The case is held against a solid, non-movable block of steel that doesn't move in relation to the cutter. It is very consistent.