Case Trimming - Needed?

[West2East]

I bought a Lyman Case trimmer. So far I have only processed 300WSM on it. My problem is that the pilots do not stay in the trimmer, it seems the set screw is not actually doing anything. Is this a thing with Lyman trimmers or is it just mine?
So it makes me wonder, is trimming needed?
Also, if you trim, what is your variance on case length that you're okay with. I mostly do 300WSM I usually trim every firing but I'm not doing much. I'm hoping to start my 6.5CM soon. and will be doing much more with that as it is my main shooter.

 

[wapitibob]

I have the Lyman trimmer, no issues but haven't trimmed brass for the last 3 firings on the STW. Neck size only as well. This ADG 7PRC brass is so short I doubt I will ever trim it. I used to think it was important, so far my groups show me it isn't.

 

[Hydra6]

I ran the same Alpha 6 Dasher brass for 19 loadings and never trimmed. I chamfer in/out after sizing so maybe the chamfering removes enough brass. Never trimmed Hornady 65CM brass or Lapua 65x47 (25x47) either.

 

[ResearchinStuff]

It really depends on the cartridge and your chamber. Steep shoulders grow slow, shallow ones grow fast.

 

[West2East]

It really depends on the cartridge and your chamber. Steep shoulders grow slow, shallow ones grow fast.

By "grow slow" at what length and in what variance do you trim? Trim at cartridge max and trim to min?
My stick is that none of them grow the same, so it's a variance after the firing. I have no problem not trimming until book max, But then I would assume you'd trim all of those in that "firing" group down to book min.
Or do you wait until the average is at book max?
Or do you not care? haha

 

[pods8 (Rugged Stitching)]

It really depends on the cartridge and your chamber.

To expand on this, if the case gets too long for your chamber when you close the bolt the brass at the case mouth gets compressed and would squeeze the bullet more which could cause pressure spikes.

 

[pods8 (Rugged Stitching)]

By "grow slow" at what length and in what variance do you trim? Trim at cartridge max and trim to min?
My stick is that none of them grow the same, so it's a variance after the firing. I have no problem not trimming until book max, But then I would assume you'd trim all of those in that "firing" group down to book min.
Or do you wait until the average is at book max?
Or do you not care? haha

You can use book max or if you really cared use a borescope in your chamber to get a longer max.

I personally don't chase trying to make every case the same length, if they are below trim length I load them, if they are over trim length I trim those.

 

[NWBLKTAIL]

I personally don't chase trying to make every case the same length, if they are below trim length I load them, if they are over trim length I trim those.

I did when I first started, now I do this is as well. Load and go shoot.

As long as I’m not over book max I’m not worrying about it

 

[West2East]

My only personal experience is a friend who is very OCD with reloading. 3-5shot groups, seating depth, ladders all of that. I'm reloading because 1. it is cheaper for the 300WSM over the $90/box of ammo and because of volume I shoot the 6.5. So I have no interest in getting that involved, nor do I think it's needed.

 

[Pescetism]

It isn't just yours, my Lyman trimmer did the same thing but only after several thousand pieces of 223 and 300 BLK. After bending out a few necks due to the pilot sticking it was replaced.

As a general statement, yes, trimming is needed but the frequency will depend on several variables.

Trimming back to book min after "fire forming" to my chamber gives me 2-4 firings before needing to trim again with most of the cartridge/brass/chamber combos I'm using. I'm not concerned with case length variation unless I'm seeing exaggerated growth.

 

[ResearchinStuff]

For me, if any are at or over Max all are getting trimmed. More often if any get close enough to where they'd exceed max on the next firing they all get trimmed.

I have not seen any evidence that different length necks cause groups to grow, but one case that's too long can really ruin your day.

 

[NorthIdahoDude]

I use one of those Frankford Arsenal Platinum Universal trimmers. Indexes on the shoulder, and makes super-short work of trimming. I tend to trim mine to dead-minimum spec, (sometimes even a hair under), and then run them till they hit max trim length in spot-checks (usually takes 3-4 firings for most things).

Trimming is one of those things that doesn't really matter... until it matters a lot (case gets long enough, brass wedges in throat, pressure spike, possible very bad day).