Question on the .357 Magnum


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Geronimo45
August 29, 2007, 09:46 PM
After getting a Model 65, I bought one of the 250-round bulk packs. Now, I've graduated to buying .357 Magnum for the gun. The .357s aren't that much taller than the .38s... but the band that's about 2/3rds of the way north of the rim is puzzling me. Is is just there for style ("how can you tell that's a magnum?" "'Cuz it's wearin' a garter"), or does it serve a useful function?

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vanilla_gorilla
August 29, 2007, 09:48 PM
Band? Does it look like the case is swollen slightly up to that point, is that what you mean?

Got any pics of what you're talking about?

Geronimo45
August 29, 2007, 10:13 PM
Here it is. Not really a band... more like a belt - to pull the insides in further.

CMcDermott
August 29, 2007, 10:23 PM
Case body crimp to prevent the bullet from being pushed further into the case. This is sometimes done to ammunition that is meant for tube magazine rifles so that the recoil when a shot is fired and subsequent impacts inside the tube magazine among the cartridges don't push the bullets into the case. With lots of lever action rifles now available in 357 & 44 Magnum some ammo manufacturers now add this crimp.

rbmcmjr
August 29, 2007, 10:29 PM
It's called a cannelure and is designed to keep the bullet from seating deeper into the case. http://www.bulletswage.com/hct-1.htm

Rick

Geronimo45
August 29, 2007, 10:39 PM
Ah... thanks a lot.

1911Tuner
August 30, 2007, 04:46 PM
The crimping cannelure is there to prevent the bullet jumping the case under recoil...forward/out...not deeper in...when the gun is slammed backward and the bullet obeys Newton 1A and stands still. Not as much of an issue with lighter bullets as with heavier bullets. Also not as much of an issue in .357 Magnum as with the .41s and .44s rounds. When you step up into the .454 Casull class, a firm crimp into a deep cannelure is critical.

rbmcmjr
August 30, 2007, 06:26 PM
The crimping cannelure is there to prevent the bullet jumping the case under recoil...forward/out...not deeper in..

Ordinarily, I would agree with you. But the cartridges he posted clearly had a cannelure on the case and the bullet:

http://www.thehighroad.org/attachment.php?attachmentid=63137&d=1188439947

The term cannelure applies both to crimping grooves in the bullets and a "milled" ring in the brass to prevent setback. The brass one is useful when shooting something with a tubular magazine, like a Winchester '94. The link I posted ( http://www.bulletswage.com/hct-1.htm ) is for a tool that can apply either.

Rick

1911Tuner
August 30, 2007, 06:30 PM
Cannelure on the brass is an extra step that locks the bullet in place...front and rear....as extra insurance. Not all ammo mamufacturers do it. Why would a revolver round need to have a cannelure to prevent bullet setback? They don't go through a full-speed, violent feed cycle like autopistols do.

Majic
August 30, 2007, 07:24 PM
a "milled" ring in the brass to prevent setback.
The cannelure is not milled into the brass. It's pressed into the brass using a set of dies.

rbmcmjr
August 31, 2007, 01:58 PM
Why would a revolver round need to have a cannelure to prevent bullet setback?

Because when they are in a tubular magazine, they are subjected to setback forces? Not that there are that many people who use them for that, but obviously that manufacturer chose to use them.

The cannelure is not milled into the brass.

That's why I used quotes around the word to denote a misused but similar term. Milled is the word used to describe the edges of dimes and quarters, which is the effective appearance of the cannelure.

Rick

1911Tuner
August 31, 2007, 02:40 PM
Because when they are in a tubular magazine, they are subjected to setback forces?

Try using .357 ammuntion without the rearmost cannelure in a tubular magazine and see if the bullets set back. They won't. The roll crimp into the bullet's cannelure is sufficient to prevent it. Even in this day of .44 Magnum lever-action carbines, it's pretty much unnecessary.

Back in the day...when Remington and Winchester loaded the gas-checked 240 LSWC to true advertised velocities, there was a deep crimp at the base of the bullet in the case and a firm roll-crimp that positively locked the bullet into place. The only other factory rounds that I've seen that use such a procedure was some...but not all...of the USGI hardball ammo. The bullets didn't have cannelures, and because the cases couldn't be roll crimped...it was deemed insufficient to prevent setback when cycling through the Thompsons and M3 "Grease Guns" due to the massive bolts...but the roll crimp/bullet cannelure was sufficient even in the violent slam-bang actions of the Garand and M14 rifles.

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