.30 carbine case length


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Hardtarget
February 19, 2011, 11:45 PM
I'm ready to load some .30 carbine rounds. I checked my loading books. Two said to trim to 1.286. Ok, fine with me. I measured all my brass just to see how things looked.

Then I get my RCBS trim pro out to set up...the chart lists the trim length as 1.280

So...now I'm wondering...0.006 is not a LOT, but it is some difference. All I'm needing is direction. What length works? Should I just load a few at 1.286 to see if they chamber in my gun and only trim shorter if they show a problem?

I know y'all will point me in the right direction so I'll say thanks, in advance, for the help.

Mark

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Sport45
February 20, 2011, 12:00 AM
Minimum trim length is 1.280 if I recall. Anything between 1.280 and 1.290 should function in a carbine. Trimming them all to the same length will give you the most uniform crimps.

Some never trim .30 carbine, some trim to 1.280 every time. I think I trimmed my last batch to 1.285 and the trimmer barely kissed some of them.

Sunray
February 20, 2011, 12:35 AM
Don't know why RCBS would publish that length. Maybe because the normal trim-to for most cartridges is 10 thou under max. Anyway, the trim-to length for the .30 Carbine is 1.286". Max case length is 1.290". Both given in every manual I have. Been loading .30 Carbine for 30 some years and don't recall ever having to trim though.

medalguy
February 20, 2011, 12:08 PM
I trim to 1.280 and usually get 2 reloads before I need to trim again. Longer length = more trimming between reloads. Save yourself a little bit of trimming work.

USSR
February 20, 2011, 06:47 PM
I also recommend trimming to 1.280". The .30 Carbine is the "growingest" cartridge I load for, and I HATE trimming.

Don

Hardtarget
February 20, 2011, 11:52 PM
Thanks guys! Looks like I'll be trimming a few cases next time I'm at the bench. :D

The range of "trim to" lengths surprised me a bit. I will trim to 1.280 and that will even up my cases very nicely.

Thanks again for your help. This is a good group to be with!

Mark

Sunray
February 21, 2011, 12:58 AM
"...even up my cases..." That's more important anyway. And you're right. 6 thou isn't enough to worry about. The average human hair is 4 thou.

Steve Marshall
February 21, 2011, 06:36 AM
I just finished loading a batch. The longest case was 1.302". This was a LC72.
Many of the LC72's were over 1.290". On 30 Carbine brass, I measure every one prior to loading. Always. Anything more than 1.285" gets trimmed. I also suspect the case headspaces on the taper, not the OAL. One day, I will trim a case to, say, 1.200" and try it out.

ranger335v
February 21, 2011, 02:25 PM
"Should I just load a few at 1.286 to see if they chamber in my gun and only trim shorter if they show a problem?"

Well, you have the rifle and cases so it will be easy to test. It makes no difference what a book says, your ammo has to function in your rifle; if it works, it's good. If it does't, trim it. ??

cfullgraf
February 21, 2011, 04:37 PM
I also suspect the case headspaces on the taper, not the OAL. One day, I will trim a case to, say, 1.200" and try it out.

30 Carbine head spaces on the case mouth not the case taper. So, case length is important.

Cartridge overall length will be mostly dictated by the magazine in the 30 Carbine.

1.200" i assume is a typo as it is WAY TOO short.

Steve Marshall
February 21, 2011, 07:04 PM
And you know it headspaces on the case mouth how? If you already KNOW this, please tell us.

Cherokee
February 21, 2011, 08:58 PM
I trim to 1.280" which I have read is the military specification. Been loading the carbine since 1960 following that practice.

jcwit
February 21, 2011, 09:14 PM
How do we know where or how the .30 carbine headspaces? Go Here, almost all the way down.

http://www.m1carbinesinc.com/safety.html

Yes it does headspace on the case mouth.

Check here also, little over a third of the way down.

http://forums.thecmp.org/showthread.php?t=2967

jcwit
February 21, 2011, 10:11 PM
Per the CMP, trim to 1.280 to prevent the possiblity of a fire out of battery.

Steve Marshall
February 22, 2011, 07:04 PM
But all these warnings are for cases that are over max not under min. This weekend I will trim brass until it no longer fires a primed case or fails to extract. And I still suspect at some point, case taper will do the headspacing albeit short. We'll see.

jcwit
February 22, 2011, 08:23 PM
But all these warnings are for cases that are over max not under min. This weekend I will trim brass until it no longer fires a primed case or fails to extract. And I still suspect at some point, case taper will do the headspacing albeit short. We'll see.

No, it only means that the extractor is holding the round tight enough for the impact of the firing pin to ignite the primer.

This is also why the Spanish Astra M-400 chambered for 9mm Large was also able to fire 9mm Lugar. The same happens/holds true for other firearms and calibers. Ever see a 40 S&W case that had been fired in a .45 acp?

Do as you wish, don't hurt yourself in the process.

Steve Marshall
February 27, 2011, 10:59 AM
I conducted a test. Up front, all cases were sized, trimmed, deburred, taper crimped and measured, then primed ensuring the primer was flush to below. No powder or bullet was involved. THIS WAS NOT LOADED AMMUNITION. I started at 1.275" and attempted .003" increments and for the most part succeeded.
The Inland fired the primer and ejected down to 1.260". It would fire the primer down to 1.254 but not eject.
The Universal fired the primer and ejected down to 1.257". It would fire the primer down to 1.233! but not eject.
I used 12 cases in all. 1 each Federal Remington and LC72.
Each test was conducted with 1 of each case at a particular length. There was only one instance in the entire test that the result was not duplicated. @1.260" the Inland failed to fire the LC72, but did so on the second try and went down to 1.254" in further testing. Obviously no explanation. The Universal marked the primer at it's shortest length all six times. The Inland did not.
I was debating whether I should try this with live ammunition but decided against it.
On a side note, I found some LC72's that were 1.298"-1.300" after sizing. These fired in both rifles 6x6 times. I did NOT consider this with live ammunition.

For those who reload the Carbine without trimming? Good Luck. I personally believe you've been pushing said luck.

jcwit
February 27, 2011, 06:27 PM
Repeat

No, it only means that the extractor is holding the round tight enough for the impact of the firing pin to ignite the primer. This is also why the Spanish Astra M-400 chambered for 9mm Large was also able to fire 9mm Lugar. The same happens/holds true for other firearms and calibers. Ever see a 40 S&W case that had been fired in a .45 acp?

HOWARD J
February 27, 2011, 08:15 PM
Funny thing--no one mentioned the Ruger Blackhawk 30 carbine revolver--let your
cases get too long-Ruger lets you know in a hurry.

Steve Marshall
February 27, 2011, 09:12 PM
I'm going to hazard a guess that the ones that didn't eject were not having any truck with the extractor. NOW, I am convinced that the 30 carbine case headspaces on the mouth versus the taper.

jcwit
February 28, 2011, 09:41 PM
True!

Steve Marshall
March 1, 2011, 08:20 PM
So what was the non-sequitor of extractors and 40's fired in a .45?

slowbutsure
March 2, 2011, 03:54 PM
Guy's I have been reloading for the .30 about 8yrs now. One day about two years ago, I called and spoke to Speer, about their trim data in the #13 manual. I asked why so much trim (.010)? I was told that it was simply a length that was used in their testing, and that trimming could be less if I wanted to do less. Keeping in mind of course the max case length. Then the #14 manual came out and now recommends a trim at .005". Which, seems to me a better recomendation. At any rate, I had started, after my coversation with them, to trim at .005". I have not seen any problems in any of my two .30's. And yes the .30 does headspace on the case mouth. Sbs

Note: The Hornady manuals #6 and #7 still show a trim at .010". My Lyman manual #49 shows a trim to lenght of 1.286"........SOOOOOOOOOOOO? sbs

Sport45
March 2, 2011, 08:24 PM
So what was the non-sequitor of extractors and 40's fired in a .45?

It wasn't a non-sequitor. Just an example of how the extractor can hold a cartridge against the breech face for firing in spite of the case being much too small to properly headspace.

zxcvbob
March 2, 2011, 08:30 PM
The trick with .30 Carbine is you have to measure the cases *after* resizing them. That's when they [sometimes] lengthen. They don't lengthen when fired; they sometimes even get shorter (and fatter.)

I was really scratching my head until I figured that out (I have a Ruger .30)

Hardtarget
March 3, 2011, 12:41 AM
This has been good. Info and comments and experience with the round I'm wanting to load. This is what makes THR a good web site / shooter board to come to!

Thanks! great stuff.

Mark

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