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Springback
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Picture of woods
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Lately I have seen a couple of references to there being more springback on work hardened or several times fired cases. This seems counterintuitive to me and I think that work hardened brass loses it's springback and that new or freshly annealed brass has the most springback.

That is the only thing that would explain the following:

1. On my tight necked chambers that I have to keep track of the necks on, I find that the brass does not reach and stay at the complete diameter until it is fired at least 3 times. IOW, on a 338RUM with a neck of .386"

  • once fired necks will measure .3845"
  • twice fired .385"
  • 3 times fired .3855"
  • 4 times fired .386"
  • Every firing from then on if not annealed it will be .386"


To me this means that the necks are work hardened and not springing back from the chamber dimensions.

2. When measuring the shoulders with a headspace gauge I always get measurements similar to this

  • New case 2.040"
  • Once fired 2.0485"
  • Twice fired 2.050"
  • 3 times fired 2.051"
  • 4 times fired 2.0515"


Which indicates to me that there was much more springback when new than after 4 times fired.

Does anyone have any references or proof that new or freshly annealed brass has more or less springback?


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

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Posts: 2716 | Location: Houston, Tx | Registered: 17 January 2005Reply With Quote
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the only evidence i can give to this is that my groups will shrink back down after an annealing and a resizing.
 
Posts: 977 | Location: soda springs,id | Registered: 02 April 2008Reply With Quote
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quote:
Originally posted by woods:
Lately I have seen a couple of references to there being more springback on work hardened or several times fired cases. ... Does anyone have any references or proof that new or freshly annealed brass has more or less springback?
I think they were all using "Thingys", which EASILY explained it to me. rotflmo
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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We may have two interpretations due to perspective. One application of the term refers to how the brass responds to fire-forming. The other describes how the brass responds to sizing.


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Posts: 1184 | Registered: 21 April 2007Reply With Quote
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quote:
Originally posted by Winchester 69:
We may have two interpretations due to perspective. One application of the term refers to how the brass responds to fire-forming. The other describes how the brass responds to sizing.


Wouldn't the reactions be the same? IOW, if the brass springs back when subjected to pressure from a sizing die and springs back would be the same as being expanded during firing and springing back. The condition of the brass, either soft or work hardened would dictate how much springback would occur in each case.

I am not sure which has more springback and prefer not to simply go with conventional or often repeated statements just because someone says so. To me a statement like "work hardened brass has more springback" is similar to the statement "seating the bullet deeper into the case will create more pressure". We went through the bullet seating thing and by far more proof was presented to show seating deeper decreases pressure and would like to see if anyone has any data on the springback correlation to hardness of brass.

If not then it is still up in the air. It would be nice to at least get everyone's opinion on which it is.


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

___________________________________
 
Posts: 2716 | Location: Houston, Tx | Registered: 17 January 2005Reply With Quote
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I think the answer to this question is explained by an understanding of several materials topics.

1. Young modulus or the modulus of elasticity
2. The elastic limit of a material
3. The fit of an unfired case vs the fit of a fired case. This is the distance the material is strained before it yields.

I think I know the answer but I need to verify it before I stick my neck out any further.


.50-70 - The only Government I trust
 
Posts: 12211 | Location: http://www.tarawaontheweb.org/tarawa2.jpg | Registered: 03 December 2008Reply With Quote
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A parameter has been chosen to judge the effects of two processes. This parameter is formally known as an operational definition. Then we have applied a label, springback, to describe the parameter. I'm suggesting that the commonality is the label. The processes are dissimilar, as are the operational definitions. The brass has work hardened, but we have not said how it is related to springback; such a statement would constitute an hypothesis. Working with two processes, we would need two hypotheses.

I realize that what's been stated here only confuses the discussion, but it accurately describes the problem.

The solution is in recognizing that fire-forming and sizing are independent processes imposing different forces on the brass. Likewise, the reaction of the brass will be different. The measurements are indicative of the independent processes and not solely the condition of the brass.

Perhaps an additional statement will help. One of our processes is stretching the brass. The other is shrinking the brass.


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Posts: 1184 | Registered: 21 April 2007Reply With Quote
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quote:
Originally posted by Winchester 69:

Perhaps an additional statement will help. One of our processes is stretching the brass. The other is shrinking the brass.


Okay, I can see the difference there and it makes sense that they would be different. However if you were using an expander ball type of die that would be similar forces on the neck in that it is expanding the neck brass outward like fire forming, but the case body would be "shrinking" from the die sizing the body. With a Lee Collet the neck brass would be forced inward and then spring back outward. Those would be dissimilar.

quote:
Originally posted by SR4759: I think I know the answer but I need to verify it before I stick my neck out any further.


You won't find me busting your chops for a wrong answer. Winchester's answer has already started me thinking. I have to ferret these things out in my head before I can come to a conclusion.


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

___________________________________
 
Posts: 2716 | Location: Houston, Tx | Registered: 17 January 2005Reply With Quote
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We're making a lot of assumptions regarding the process based on a single measurement. It's necessary to fully understand a process rather than to sample it. Remember the old story about the blind guys and the elephant?

The process defines the parameter (read: operational definition) rather than vice versa.

Speaking of elephants, I heard a joke yesterday that I've been looking for an opportunity to share. It was in a movie that was so bad I doubt if anyone heard the joke.

Q: What do you do with an elephant that has three balls?

A: You walk the elephant and pitch to the rhino.


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Posts: 1184 | Registered: 21 April 2007Reply With Quote
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Great avatar, woods...
 
Posts: 16534 | Location: Between my computer and the head... | Registered: 03 March 2008Reply With Quote
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A long time ago someone suggested to me that I properly anneal a 6ppc case that had been fired 5 times and size it and then size in the same FL die, another case from the same lot that had not been annealed, then let them sit for two weeks. When measured, at the end of that time there were interesting results and a lesson as to what ductility means in forming metals.

This was in connection with this same subject and a related one: whether it was worthwhile to load on the tailgate at matches and how hotter loads would "set" brass more quickly. A lot of BR shooters at that time were forming cases with very hot loads and then resizing as many as 4 or 5 times at a match, where they were firing pretty hot loads too, then discarding the brass.


If the enemy is in range, so are you. - Infantry manual
 
Posts: 494 | Location: The drizzle capitol of the USA | Registered: 11 January 2008Reply With Quote
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So does that mean that brass loses springback as it gets work hardened or gains springback as it gets work hardened? Confused


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

___________________________________
 
Posts: 2716 | Location: Houston, Tx | Registered: 17 January 2005Reply With Quote
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quote:
Originally posted by woods:
So does that mean that brass loses springback as it gets work hardened...


Yes.

Don




 
Posts: 5798 | Registered: 10 July 2004Reply With Quote
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Here is another thought: A lot depends upon the actual alloy of the brass, whether it was PROPERLY annealed before working, and how hard you've worked it in the first place. Something noticed by many of us during the Great Lapua Outsourcing Debacle of some years back was that premium brass such as Lapua or Norma and now Nosler comes from the factory very much uniform in size and capacity. Standard brass such as Winchester, RP, the stuff Lapua bought back then, or Federal is not nearly so uniform out of the box. If you want an idea as to how important that is call up one of the premium brass makers who will cheerfully guide you toward a diving board where you can go jump in the lake should you ask them to reveal their alloys or annealing processes.

It has been my experience that brass springback, or rebound, works both ways and especially as the brass becomes work hardened, the brass becomes more and more reluctant to assume the shape I want it in. This is because the brass has lost ductility, that being the word describing a metal's "willingness" to be worked into shape. Therefore, it is hard to say how a given case will react to sizing and also easy to understand why experienced match shooters buy as much of a good lot of premium brass as they can, or buy fully formed, trimmed, and neck turned brass from folks like Lester Bruno, use it a match, where they may FL size it 5 or more times, and then discard it. Those of us who don't have such financial independence must learn how our brass reacts after so many sizings and annealing and etc.. It seems to me it is easier to deal with premium brass when real accuracy is critical than to suffer the woes of false economy by buying standard brass. For plinking, or short range hunting I don't think it matters.


If the enemy is in range, so are you. - Infantry manual
 
Posts: 494 | Location: The drizzle capitol of the USA | Registered: 11 January 2008Reply With Quote
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Woods ; By all rights there should be LESS spring back on freshly annealed cases !.

They are their softest before becoming work hardened . IMO archer
 
Posts: 4485 | Location: Planet Earth | Registered: 17 October 2008Reply With Quote
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quote:
Originally posted by Doc224/375:
Woods ; By all rights there should be LESS spring back on freshly annealed cases !.

They are their softest before becoming work hardened . IMO archer


popcornMe 2 Roll Eyesroger


Old age is a high price to pay for maturity!!! Some never pay and some pay and never reap the reward. Wisdom comes with age! Sometimes age comes alone..
 
Posts: 9199 | Location: Temple City CA | Registered: 29 April 2003Reply With Quote
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So we have

2 for less springback with work hardening
2 for less springback with new or annealed cases
1 to walk the Elephant and pitch to the Rhino Big Grin

popcorn


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

___________________________________
 
Posts: 2716 | Location: Houston, Tx | Registered: 17 January 2005Reply With Quote
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quote:
Originally posted by woods:

1 to walk the Elephant and pitch to the Rhino

Ain't democracy grand? patriot


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Posts: 1184 | Registered: 21 April 2007Reply With Quote
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quote:
Originally posted by woods:
So we have

2 for less springback with work hardening
2 for less springback with new or annealed cases
1 to walk the Elephant and pitch to the Rhino Big Grin
And:
1 Thingys are Full of Beans
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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Where can I shoot me one o' them springboks? rotflmo
 
Posts: 646 | Location: Chester, Home city of the Green collars. | Registered: 14 February 2006Reply With Quote
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It has always been my opinion that new and annealed brass has less springback.

However, it seems as though there is some difference in opinions as to what constitutes "spring back", and possibly "work hardening".

To me a text book example of spring back is when my 22-250 cases get work hardened. I neck size using a Lee collet die, and have to put way more pressure on the handle to get the case mouth to grip the bullet. If I don't push down hard, the mouth springs back. After annealing, it takes much less pressure to achieve the desired grip. The difference is quite noticeable.

Jim


Please be an ethical PD hunter, always practice shoot and release!!

Praying for all the brave souls standing in harms way.
 
Posts: 731 | Location: NoWis. | Registered: 04 May 2004Reply With Quote
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If you poke pin gauges into the necks of the chamber and the die, you can determine the inside diameters.

If those numbers are close, there will be little or no work hardening.

I have been buying small neck reamers and large neck dies.
 
Posts: 9043 | Location: on the rock | Registered: 16 July 2005Reply With Quote
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Well I ran into this in American Rifleman May 2009 issue, article on Smith & Wesson's 460XVR on page 54

quote:
Had Hornady's engineers not had prior experience loading the .454 Casull, the 460 S&W Mag.'s case would have presented another dilemma. With pressures similar to those of the .454 Casull and production-type revolvers using the new cartridge, Mittelstaedt determined the cases needed to be "cold worked" to the brass' limits, which resulted in maximum strength/hardness, as well as better "springback". Spring back is the case's ability to, under high pressure, expand to the size of the chamber then retract enough for easy extraction. "Soft" brass doesn't "spring back", making extraction difficult.


Guess I have to start trying to work this into my brain and figure out why.

popcorn


____________________________________
There are those who would misteach us that to stick in a rut is consistency - and a virtue, and that to climb out of the rut is inconsistency - and a vice.
- Mark Twain |

Chinese Proverb: When someone shares something of value with you and you benefit from it, you have a moral obligation to share it with others.

___________________________________
 
Posts: 2716 | Location: Houston, Tx | Registered: 17 January 2005Reply With Quote
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