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Old February 12, 2013, 07:40 AM   #1
brianl
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Minimum Case Length .308

I have browsed many gun sites but still have no clarity on this. My case length trimmer reduces my case length to 50mm. What is the minimum case length for this round? All answers that I have is that one must ensure that at least one third of the bullet is seated in the catridge case. This then brings me to ask what is the minumum round length of the .308

I am quite sure that my 50mm cases are fine but there must be a cut off lower limit such as the max length. Any comments?
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Old February 12, 2013, 08:36 AM   #2
steve4102
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This should be in your manuals. What manuals do you have?

Max case length=2.015 inches.

Trim-to-length=2.005.

"All answers that I have is that one must ensure that at least one third of the bullet is seated in the catridge case."

Never heard this before, maybe because it is wrong. The rule of thumb is that one bullet diameter be seated into the case. That would be .308 inches be seated into the case of your 308 Win.
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Old February 12, 2013, 08:41 AM   #3
Brian Pfleuger
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I've never heard of "1/3" bullet seating. A general starting point is one caliber length but even that's entirely generic.

Your bullet should be seated so it fits and functions in your gun.

For a new reloader, it is wise to stick with the length specified in the data until you have a understanding of what happens when you change it.
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Old February 12, 2013, 08:52 AM   #4
Rainbow Demon
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The Boers had problems with a batch of 7X53 mm cartridge cases they got among smuggled shipments of 7X57 mm ammo.
The 4mm gap was enough to let a bullet upset and expand enough that the rear of the jacket could seperate and shear off. When the next round was chambered the bullet telescoped inside the ring of jacket material jamming it in the throat and caused excessive pressures that Kaboomed a few Mausers.

A 1mm gap is unlikely to cause any safety issue, but if accuracy is affected you should correct the issue.
A case trimmer should have some sort of adjustment feature.
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Old February 12, 2013, 09:00 AM   #5
Brian Pfleuger
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The Lee Case Length Gauge and Cutter is a very simple device which trims cases to a fixed length, the "Trim to" length listed in most data.

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Old February 12, 2013, 10:03 AM   #6
higgite
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OP says his trimmer reduces his case length to 50mm. That's about .026" shorter than SAAMI minimum. Is that acceptable to you experienced reloaders? Or is the SAAMI minimum a "never go less than" number? I treat it that way, but I'm a relative newbie reloader and don't feel safe wandering outside standard dimensions.

Edit after Brian's post #7.: SAAMI minimum OAL that I was referring to is 1.995" (50.67 mm).

Last edited by higgite; February 13, 2013 at 10:25 AM.
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Old February 12, 2013, 10:29 AM   #7
Brian Pfleuger
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Lyman 49th lists the Trim To length of .308Win as 2.005 inches. That is 50.927mm.

I'd like to get an exact measurement from the OP. Is it "50.0mm" or is it "roughly" 50 and more like 50.5, 50.75?
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Old February 12, 2013, 11:13 AM   #8
Bart B.
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Trimming .308 cases to 1.9685" (50mm) won't hurt anything, but it'll be a reason to clean the chamber mouths very good. I've kept mine from 2.000" to 2.010" and trimmed 'em when at the upper limit back to the minimum.

I've seen all sorts of "standards" for bullet seating depths from some fraction of every round's dimensions possible. In reality, as long as the bullet's held secure enough for environmental handling and loading, pick the depth you smile the most with. One of my .308 Win. match barrels started out with 190's being seated about 1/4th inch into the case and would shoot about 1/2 MOA at 600. I kept track of having to seat them until the throat had eroded enough so bullets' bodies were only held by about 1/100th inch of the case neck and would still shoot 1 MOA at 600 yards.

Most bullets shoot most accurate when they're touching the lands when fired; Berger's VLD ones seem to do best several thousandths off the lands.
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Old February 13, 2013, 03:25 AM   #9
brianl
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Minimum 308 Case Length

Thanks to all the pros for your comments, My Lee case length trimmer shortens the case to 50mm exactly, I find the Lee Case trimmer cutting my 300, 30-06 and 223 cases inviarably too short in my opinion. When I saw the same refelction on my 308 cases it warranted some questioning. The bore dia depth seating makes perfect sense.

I will do some loads and necessary shoots.

Appreciate the comments!
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Old February 13, 2013, 08:29 AM   #10
Bart B.
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Brian, check out this spec from SAAMI:

http://www.saami.org/PubResources/CC...Winchester.pdf

It shows that case length spec is:

2.015" -.020" (from 1.995" to 2.015")
50.18mm -.51mm (from 50.67mm to 51.18mm)

Note that SAAMI specs are voluntary; it's up to manufacturers whether or not they go along with it.
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Last edited by Bart B.; February 13, 2013 at 12:05 PM. Reason: Typist had bad math or fumbling fingers on mm specs
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Old February 13, 2013, 09:14 AM   #11
higgite
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Bart,

Your SAAMI metric measurements are off by a mm. Should be

2.015" -.020" (from 1.995" to 2.015")
51.18mm -.51mm (from 50.67mm to 51.18mm)

OP's trimmer trims to 50mm, which is shorter than SAAMI minimum, for what that's worth.
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Old February 13, 2013, 12:02 PM   #12
Bart B.
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Higgite, thanks for the head's up. I told my typist's Mommy on him and he'll probably get a spankin' for making that typo.
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Old February 13, 2013, 02:59 PM   #13
higgite
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I made a mistake once....

Seriously, thanks for your input on trimming "short". I take it that it isn't recommended, but within reason, it ain't the end of the world either.
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Old February 14, 2013, 09:38 AM   #14
5R milspec
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I've been cutting my 308 brass with a Lee cutter for years,and mine comes in at 2.005.Thats ten ( .010 ) short from SAAMI.In all truth it best to cut the case only ten ( .010 ) short than what your chamber is.For this will help your chambers throat from burning out as fast.There's not many who do from what I've read.
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Old February 15, 2013, 12:08 PM   #15
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Multi task-ers? Head space is ‘THE LENGTH OF THE CHAMBER’ from the bolt face to the shoulder of the chamber, the length of the chamber from the bolt face to the shoulder is the only useful information I find useful.

Again, I have a chamber that has an additional .016” added between the bolt face and the shoulder of the chamber, if I took the case lengthens serious knowing the chamber is longer by .016” than specifications/ammo manufacturing standards I would have a neck that is .016” too short to cover the chamber at the neck, meaning I add .016” to the case length because! the HEAD SPACE ‘chamber length is beyond field reject length’.

Then there are ‘us’ case formers, we neck up 30 cal cases to 35 cal or 338 cal. not fair, our case necks do not get thicker and or thinner when necking up or down, for the most part the necks get longer and or shorter when necking up and or down. POINT: When necking a 30/06 to 35 Whelen the neck shortens .030”, moving to 30 Gibbs, neck up to 338 then neck down to 30 cal while forming a new (2nd) shoulder, that is neck up then neck down, still the case is shorter by .030”, when measuring case length after firing the case former is never surprised the case shortens as much as .040” again, the part of the chamber that is not covered with the case is a concern for me. Moving on, the 280 Remington case is longer from the case head to the shoulder of the chamber .051” than the 30/06. Rational, it has been suggested the 300 Win Mag had a short neck, the neck of the 30 Gibbs is .217” long, that is shorten than the 300 Win mag. By using the 280 Remington case the reloader can gain case length, an increase in case length increases bullet hold and the longer neck covers more of the chamber exposing less of the chamber to hot, high pressure, metal cutting gas.

To understand is to be a multi task-er.

For all the rest there is maximum case length and trim to length with total disregard for all other information.

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