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Old June 28, 2014, 08:17 PM   #1
rrruger
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357 case length question?

I understand that shortening a case or seating a bullet too deep can change the pressure spike inside the case. In the overall case length differences between manufacturers for .357 magnum cases is there a measurable pressure difference? I have been trimming used brass and I find that 'Federal, might run 1.295 while 'Hornaday' might only run 1.245. I would not be overly concerned with a few thousands, but a difference of 5/100 seems to be a bunch.
All input welcomed.
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Old June 28, 2014, 09:33 PM   #2
243winxb
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http://www.thehighroad.org/showthread.php?t=643376 Separate brass by headstamp/length. Work up load for each.
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Old June 28, 2014, 09:48 PM   #3
Sevens
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Quote:
All input welcomed.
I love it when this nugget gets dropped.

I'm a high volume handgun handloader. .327, 9mm, .38, .357, .40cal, 10mm and .45 are the ones where I rack up the highest numbers. Been doing this for years and years and years with a whole lot of success.

The next time I trim a piece of handgun brass...
Will be the FIRST time I trim a piece of handgun brass.

My log says that today, I'm at 11,020 loaded rounds of ammo since Jan 1, 2014.

I won't clean a stinkin' primer pocket, and I won't trim handgun brass.
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Old June 28, 2014, 09:57 PM   #4
5whiskey
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Quote:
I understand that shortening a case or seating a bullet too deep can change the pressure spike inside the case. In the overall case length differences between manufacturers for .357 magnum cases is there a measurable pressure difference? I have been trimming used brass and I find that 'Federal, might run 1.295 while 'Hornaday' might only run 1.245. I would not be overly concerned with a few thousands, but a difference of 5/100 seems to be a bunch.
All input welcomed.
That is a big difference, and I've noticed quite a bit of difference in .357 brass myself. I don't pay much attention to it so long as I can get a good crimp. Of course, I also don't push the limits with my loads either. I'm usually right at starting loads for .357.

One thing to remember... Your seating die will seat the bullet to leave the same powder space in the shorter case as it will in the longer case. There will just be more brass contact with your bullet in the longer cases. Where this really makes a difference is whether you can roll crimp the shorter cases in the crimp grove properly. But case length being a little short doesn't mean insta-death because your seating die basically leaves the same amount of powder space in the short cases as in the long ones. There were stories of guys that used to load .38's REALLY HOT by seating the bullets shallow and crimping in the first crimp grove (designed to hold lube and not to hold the roll crimp). I have heard of them pushing close to .357 loadings. Personally, I'll keep my .38 .38 (maybe a little +p action, but nothing crazy) and load .357 power in .357 brass.
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Old June 28, 2014, 09:58 PM   #5
Sevens
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I should have added this with my post...
Quote:
I understand that shortening a case or seating a bullet too deep can change the pressure spike inside the case.
Any time you seat a bullet deeper inside the cartridge case such that you DECREASE the internal space for combustion, pressure increases as a direct result. It's not linear (in any way) and it's not predictable, but it is a direct result.

Here's the thing you may want to keep in mind if the discussion is about trimming brass and the varying length of handgun cartridge cases:

Trimming the brass to a uniform length or using a scattered array of differing length brass is not going to affect the internal space for combustion.

That's because the shell holder is holding the case head and the bullet seating die is placing the bullet inside that piece of brass. Neither of these two tools knows or cares what the case length is.

For sure, having all your handgun brass trimmed to the same length can get you the chance for the most consistent roll crimp -- but the shell holder and the bullet seater die will not having any clue how long the cartridge case happens to be.

For a mental picture, imagine you've got a -VERY- heavy .358" slug. Just for the description, imagine it is 200 grains. That means it's L-O-N-G compared to, say, a 125gr slug.

If you have your bullet seater die adjusted so that 200gr slug sits right in the crimp groove of a piece of .357 brass... but instead, you slip a piece of .38 Special brass in there and run the ram, what's going to happen?

The bullet is going to be sticking way out of the top of the .38 brass, but it'll still be in there. And notice -- the internal space between the two rounds you just made... will be the same. That's because the shell holder and the seater die have no idea that the brass is ANY length, they only know the brass fits in that window.
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Old June 28, 2014, 09:59 PM   #6
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Haha, my post is describing the same thing 5whisky said. He just pulled it off with far fewer words.
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Old June 28, 2014, 10:02 PM   #7
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Quote:
Haha, my post is describing the same thing 5whisky said. He just pulled it off with far fewer words.
But your description was so artistic and eloquent
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Old June 28, 2014, 10:06 PM   #8
chiefr
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Many years of reloading I too have never trimmed pistol brass unless I was forming a different case. IE 44 S&W Russian from 44 SPL.
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Old June 28, 2014, 10:18 PM   #9
noylj
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If your concern was a safety issue, wouldn't every reloading manual discuss it in depth?
The real pressure problems come from having the bullet pushed 0.15" or more deeper in the case--this does not happen while firing a revolver. Most times I see this referenced, the bullet was pushed in the case 0.25".
I have never needed to trim a straight wall case for a roll crimp as the cannelure/crimp groove is much wider/longer (?) than the difference in case lengths I have seen.
When I working on every variable to get max accuracy out of my S&W M52, I tried trimming some .38 Spl cases and sorting cases and found NO EFFECT on accuracy out to 50 yards.
The critical variables were 1) the bullet Rem. 148gn HBWC was far and away the cheapest and most accurate), 2) the powder and charge (Bullseye, AA2, and 231/HP38), 3) seating the bullet STRAIGHT (and not swaging it down) and getting a seating plug that really fit the top of the wadcutter bullet (what I found worked best was to use an RCBS expander that was slightly larger OD than most and really put a flare on the case so I could seat at least ΒΌ of the bullet in the case by hand). Variables after that, besides my own shooting ability, were buried in the "noise" of the group sizes.
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Old June 28, 2014, 10:53 PM   #10
243winxb
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This -Any time you seat a bullet deeper inside the cartridge case such that you DECREASE the internal space for combustion, pressure increases as a direct result. It's not linear (in any way) and it's not predictable, but it is a direct result.

Last edited by 243winxb; June 28, 2014 at 11:19 PM.
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Old June 29, 2014, 10:32 AM   #11
Jim Watson
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Quote:
I find that 'Federal, might run 1.295 while 'Hornaday' might only run 1.245.
In that specific example, the Hornady might be from their rubbernose ammo. They use shorter cases because of the long bullets. Cull them out and load them separately.

I once trimmed a big batch of mixed .357s so they would crimp the same.
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Old June 29, 2014, 10:49 AM   #12
Unclenick
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Jim beat me to it. It's the same thing you see with Hornady .45-70 cases. They had to shorten them so their higher BC soft plastic tipped Leverevolution bullets wouldn't exceed maximum COL and hang up in a lever gun. The .357's are the same way and were originally intended for a lever gun in .357.

For a normal .357 case the SAAMI standard has 1.270"-1.290" as the case length.

Most revolver and pistol rounds don't stick to their chambers before they back up against the breech. Without that sticking, there is no stretching. Indeed, getting fat and short, followed by resizing will actually gradually shorten them a little. My .45 Auto target load cases lose about half a thousandth of an inch each load cycle.

The only reason to trim most handgun cases is to get them all equal for more equal crimping force. Because they don't lengthen, this has to be done near the short end of the SAAMI range.
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Last edited by Unclenick; July 3, 2014 at 12:49 PM. Reason: typo fix
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Old June 29, 2014, 02:09 PM   #13
rrruger
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Thanks Unclenick and Jim, as always your explanation is direct and educational
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