Case Length Variance

[Mikej]

true,
rethinking my position on this you may have a point here as long as you stay within the saami tolerance it probably doesnt matter or affect case life. I was just thinking that if the case is kept farther back then by removing more material it weakens the case faster but now Im not certain. Appreciate your input here.

their might still be an advantage to trimming less for more neck tension.

I have to believe that loading book specs are citing SAMMI specs. No?
I could be mistaken. My experience is limited to only three rifle/shouldered rounds.
A person has to always consider that loading data is just the best samples/choices of what the book authors came up with at the test lab.

 

[Movie Man]

The number itself doesn't really matter, but keeping all cases a uniform length does. More so in a cartridge that receives a crimp.
I've always been kind of surprised that not all loading manuals provide a "trim to" length.

This makes sense and kind of the direction i was heading. Just figured it would be consistent between manufacturers due to rifle specs. I know .01 really isnt that much.

 

[homeuser6]

i have shortcuts to each of the SAAMI PDFs on my desktop since i refer to them often. min/max for chambers and cartridges.
read the print ! ( a machinist would say )

 

[Koda]

I have to believe that loading book specs are citing SAMMI specs. No?
I could be mistaken. My experience is limited to only three rifle/shouldered rounds.
A person has to always consider that loading data is just the best samples/choices of what the book authors came up with at the test lab.

I would agree that loading books cite saami spec, but the issue is when the authors change their interpretation of the saami specs. The subject of this thread is evidence, and so is the prolonged discussion on what the "target" dimension is to trim to.
The loading manuals should not be citing a different dimension and tolerance than saami, that way its on the user to interpret that definition. Eg: Barnes data for 270 is -.010 the saami target dimension and they dont cite a tolerance. That is what causes the confusion.

 

[Koda]

This makes sense and kind of the direction i was heading. Just figured it would be consistent between manufacturers due to rifle specs. I know .01 really isnt that much.

at the end of the day as long as your within saami spec -and- your consistent your fine. I trim to -.005" from max length so I can account for tolerances in my trimming (+/-.005 but I usually stay within +/-.002"). (I did experiment once with a case I trimmed shorter to align the case rim with a cannelure for better crimping, which worked fine. In the end I abandoned that recipe though)

 

[Koda]

i have shortcuts to each of the SAAMI PDFs on my desktop since i refer to them often. min/max for chambers and cartridges.
read the print ! ( a machinist would say )

Same. Saami specs are free and the only thing I would use for case prep.
I make prints for a living so Im well aware how industry standards get misinterpreted thru well intentioned 3rd party publications (eg nosler vs barnes).

 

[Movie Man]

Why? Unless you are concerned about .005"+/- case length difference? Or the neck tension?

I only use two books, The Speer 14 and Lyman 50th. Speer is 3.539"-2.549". And Lyman is a "Trim To" of 2.540". I read any source, with only one case length, as a TRIM TO length, and maximum case length would be .010" more. For my type of shooting, casual, 100 yards, just havin' fun kind of shooting, a couple/three thousandths doesn't matter to me as long as it within that ten thousandths range. (roll crimped cases accurate trim length means more) You mentioned above that you're getting pretty anal about getting one hole groups at REAL distance? I would suggest that getting that anal over a couple of thou on your case trim is something you don't need to worry about, if at all, until you have done everything else to get accuracy first.

Thank you for your response.

I'm just getting started down the road of reloading. I have in my life reloaded axactly 38 rifle rnds. So things that are not consistent or confusing in a process that has some potentially dire consequences ( in my mind) I ask questions about. I want to understand variables and effects those differences and variances may have on the end result. This will help me improve overall and improve what I end up loading. What to spend meticulous time on and energy on or not.

I'm not a long range shooter or really worried about a one hole grouping but isnt that what we all really try to strive for? Probably never will be a long range shooter, consistency yes, accuracy yes, cheaper yes (although this aspect seems questionable right now....lol).

I'm finding from responses and yours this small difference in length doesnt matter as long as it's within saami specs and all your cases are consistent in length. Which is good to know when looking at different load books with conflicting or different information.

 

[Mikej]

Eg: Barnes data for 270 is -.010 the saami target dimension and they dont cite a tolerance. That is what causes the confusion.

Well, this tells me that SAMMI say you can't go over "This" length. I will assume, because, too long of a case causes problems. 10 thou under will not/should not, affect anything? I figure, it's just become common at some time to use this -10 thou variance ?

I DO see where confusion comes in now. I looked at Hodgdon web-site and their data for .270WM gives 2.539" "Trim Length" Not Trim to Length". Nor does it give a max length. I will continue to take the Speer book's Trim To and max length and stay somewhere between the two. Trimming for uniformity of the cases.

 

[Mikej]

Thank you for your response.

I'm just getting started down the road of reloading. I have in my life reloaded axactly 38 rifle rnds. So things that are confusing in a process that has some potentially dire consequences ( in my mind) I ask questions about. I want to understand variables and effects those differences and variances may have on the end result. This will help me improve overall and improve what I end up loading. What to spend meticulous time on and energy on or not.

I'm not a long range shooter or really worried about a one hole grouping but isnt that what we all really try to strive for? Probably never will be a long range shooter, consistency yes, accuracy yes, cheaper yes (although this aspect seems questionable right now....lol).

I'm finding from responses and yours this small difference in length doesnt matter as long as it's within saami specs and all your cases are consistent in length. Which is good to know when looking at different load books with conflicting or different information.

Even I was a little spun around here! I must have been thinking of another member that was going for the elusive "One-Ragged-Hole" thing.
Good Times Man!

 

[Movie Man]

To all responders in this thread.....thank you!

I really want to thank everyone for the input and discussion. For me its been good to read, hopefully other too getting into this hobby.

 

[Stomper]

These types of threads are the largest argumentative NERD magnets, EVER!

 

[Mikej]

These types of threads are the largest argumentative NERD magnets, EVER!

Yeah? And if the discussion was around HVAC you'd be ALL over it!

 

[Koda]

Well, this tells me that SAMMI say you can't go over "This" length. I will assume, because, too long of a case causes problems. 10 thou under will not/should not, affect anything? I figure, it's just become common at some time to use this -10 thou variance ?

I DO see where confusion comes in now. I looked at Hodgdon web-site and their data for .270WM gives 2.539" "Trim Length" Not Trim to Length". Nor does it give a max length. I will continue to take the Speer book's Trim To and max length and stay somewhere between the two. Trimming for uniformity of the cases.

Yes, this is where confusion comes from. Now we find Hodgdon uses yet another callout on trim length. Were literally seeing the "grapevine" effect take place. The reloading manuals should know better IMO and should all cite the saami spec exactly, that way the individual can interpret that to fit his application rather than establish a different method based on how one manuals author does it.
I'm being my usual over analytical self here, but because I make blueprints for a living I'm just well aware of the nuances to industry standards and the use of a unilateral tolerance means something different than the common symmetrical tolerance.

 

[Koda]

These types of threads are the largest argumentative NERD magnets, EVER!

Im glad we caught your attention...

 

[Mikej]

I'm being my usual over analytical self here,

That's the best way to be. And after analyzing the bubblegum out of something you will, hopefully, realize what the safe tolerances are and go about business!

Im glad we caught your attention...

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"Geek" and "Nerd" are no longer putdowns in my book. They are terms of endearment! Geeks and Nerds RULE!!!

 

[Koda]

That's the best way to be. And after analyzing the bubblegum out of something you will, hopefully, realize what the safe tolerances are and go about business!

"Geek" and "Nerd" are no longer putdowns in my book. They are terms of endearment! Geeks and Nerds RULE!!!

at the end of the day its the "nerds" that determine what everyone else gets to do.
Safely anyways....

 

[Koda]

@Mikej I learned something from you here regarding trim length affecting case life and appreciate your input there. Im no longer certain it affects case life so now the "nerd" in my is left wondering why the saami engineers used a unilateral tolerance on case length. Im thinking now maybe uniform chamber pressure, carbon ring reduction, better case sealing when fired. Who knows any guess is as good as mine.

 

[Mikej]

Im thinking now maybe uniform chamber pressure, carbon ring reduction, better case sealing when fired

I'd say, yes? that seems like common sense.
What I lack in intelligence I try to make up for with common sense. That's about all I've got up stairs.

 

[Stomper]

Yeah? And if the discussion was around HVAC you'd be ALL over it!

Nope, over 34 years in the trade (5.5 more to go)…. and I'm so over it. I tell people (on a daily basis), "don't ask me, I'm wearing my IDGAF shirt".

 

[Stomper]

Im glad we caught your attention...

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Hey, I like a good train wreck the same as the next masochist!