Flared Case Mouth Rebound?

R

robhic

New member
I just made up about 20 .38spl rounds. Random cases from my "stash", Bayou Bullets Hi-Tek coated 124gr round nose bullets. Using my RCBS RockChucker and RCBS dies.

Sized cases and re-primed. Swapped dies for flare. I don't like to flare too much so I did a little at a time until the bullet just fit in the flare. Did all 20, charged with powder and swapped dies to seat. I had checked bullets in random cases to verify flare-fit during the flaring process.

Finished flaring, priming and charging so put the bullet in the first case to seat and bullet was not such a good fit. :confused: So I tried another bullet to see if maybe the first was a bit out of spec. Nope, still a bit too big.

Tried other cases and same problem. So I put in the flaring die (again) and re-flared all 20 cases a bit more than first go-round. This time it stuck.

Has anyone had what seems to me to be the case returning to a reduced size (rebound?) after flare? Is the brass that malleable and/or elastic to actually return to a smaller size after the flare? That's all I can figure so if ya got anything on this or some other explanation I'd be curious to hear it cuz this is weird and hasn't really happened before. Thanks!
 
Perhaps when you previously screwed that flare die in and out last time, maybe you moved the setting? I have done that with certain dies when I get complacent and rush a tad.
 
Perhaps when you previously screwed that flare die in and out last time, maybe you moved the setting? I have done that with certain dies when I get complacent and rush a tad.
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I didn't really move the flaring portion. I lightly locked the die body and started running cases up then trying a bullet for fit. After I had a few that seemed OK (not too wide...) I lightly locked down the flaring stem. Nothing should have moved.

I keep thinking about how some materials (especially metals) need to be bent a bit further than needed so as to have it right because the material springs back a bit.
 
Poly coated vs Jacketed or plated always requires a tad more flare. So if seems for me. I've never had brass bounce back after a flare.
 
The brass does not creep back to a previous form like some plastics might.
If you think about the force a lock ring applies,its in the direction that might subtract crimp.
As with wingshooting,it can be necessary to "lead" the adjustment a bit before locking down to get the final result.Whatever works.Check results after lockdown.

Of course,having your cases at uniform length is critical to consistent flare and crimp.
 
Flair Rebound?

I think they do.

It's something I've pondered and even thought about creating a post (like this one) asking if others have noticed.

Here's my story (try to be brief, as this is not my post):

I flair generously. And I prep my brass for reloading first; and then stash them in my Folgers coffee cans until I need to load them. Sometimes, I go to use brass that I reconditioned months or even years before. It seems whenever I get ahold of older ones especially, there is barely enough flair to get the bullet started - even though I know I gave them a generous flair.

I know it's unscientific. But it seems that whenever I grab brass that was reconditioned a long time ago, that they have less flair - even though I haven't touched my flair die(s) settings in I don't know how long.
 
Flaring puts stress in the metal and that stress will try to relieve itself by pulling the brass back, especially if it gets shocked or knocked around. It's the same reason springs eventually take a set; the metal changes toward the stressed shape in that case because the spring is constraint to its position, but with stress and no constraint there is shifting over time.
 
Is the brass that malleable and/or elastic to actually return to a smaller size after the flare?
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Well, of COURSE THEY ARE! :D

The elasticity of brass it the reason its used for cartridge cases in the first place. Its what allows extraction of the fired case after being "hammer welded" into the chamber by tens of thousands of pounds of pressure. The brass springs back, slightly.

Do you think its NOT going to do that when its expanded or compressed by a sizing die? Die makers know this, too, and cut sizing dies accordingly.

Sounds like you just hit the "perfect storm" of just barely enough adjustment and a bit over average springback. The elasticity of brass will vary with the alloy, and even different lots from the same maker can vary a bit. Usually its not enough to notice, sometimes, it is.
 
Sounds like you just hit the "perfect storm" of just barely enough adjustment and a bit over average springback. The elasticity of brass will vary with the alloy, and even different lots from the same maker can vary a bit. Usually its not enough to notice, sometimes, it is.
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Jump back, snap back and spring back and now we add rebound; jump, snap and spring back are non factors. About the time a reloaders thinks he has it all worked out he is up to 5 firings; at 5 firings I have to remind them it is time to start over by going to full length; and I wonder how is it possible to start over with a case that has been fired 5 times because snap, jump and spring back has changed.

I have fired cases with heavy loads, after firing the case did not have spring, jump, snap back or rebound. The cases were hit so hard they only had one way to go' that would be forward and backward. And because of the shortage of jump back the cases were difficult to extract.

To me it is not 'oddly enough' the primers pockets got loose, it had nothing to do with soft headed cases; it had to do with heavy loads. A normal factory load can expand the case head .00025" and then? if deductive reasoning is applied the reloader can assume with a factory load the case head will expand .001". with 4 firings. Again, I have expanded case heads .001" with 1 firing;.

Do I get excited about case heads that do not expand?:eek: I had rather have a case head that will expand than one that will not expand, again, as Martha says; "and that is a good thing".

F. Guffey
 
Flaring puts stress in the metal and that stress will try to relieve itself by pulling the brass back, especially if it gets shocked or knocked around. It's the same reason springs eventually take a set;
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That was my thought. Having had to over-bend something to have it return to a lesser bend is what I considered. Like bending a piece of metal 92° (example only) so when you stop bending the metal will 'return' to 90° which was what you wanted. I thought I was flaring too generously and figured I'd do a bit less. I flared until the bullet fit enough to (hopefully) not shave. Then I flared the rest of those 20 cases to that size.

I suppose I didn't consider 'springback' (or pick your term) and after 20 minutes elapsed and I went back to put the bullet back in the case it had receded a bit. I've not had this before and since I thought my flares were too generous, I might've actually been solving this problem and didn't realize it!

The elasticity of brass it the reason its used for cartridge cases in the first place. Its what allows extraction of the fired case after being "hammer welded" into the chamber by tens of thousands of pounds of pressure. The brass springs back, slightly.
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Now that, right there, is what I should have thought about. "Obduration" (see, I'm gettin' the hang of this stuff... :D) in itself explains the return to smaller size. I had flared too tightly and even a slight return messed up my flare!

Thanks to all for making me realize what I shoulda thought about in the first place. Duh! :(
 
Take it from a metallurgist folks, no, the brass does not creep back. When you stress metal into the plastic region, then release the stress, there is an immediate "rebound" of the elastic deformation. That's it. There are internal stresses created - work hardening - but those will not be released at anywhere near room temperature. You would have to heat the metal - anneal it - to relieve the stress. And unless you grossly overheat, even that will not change the dimensions.

Think about it. How would we ever form an auto body if an hour later it changed shape?
 
I believe all brass has a tendency to "spring back" when worked (called "memory"). I recommend new reloaders use as much flare as needed to easily seat a bullet, and worry about case "life" later. Get good shootable ammo and worry about case life later and 38 Special is readily available and cheap. The only "problem" from large flares is the case mouth will rub on the ID of the seating die. When you work out the "kinks" of reloading you can lessen the flare...
 
I believe all brass has a tendency to "spring back" when worked (called "memory").
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How does that work? I said I have fired cases with loads that were so heavy the case could not remember what it was before I pulled the trigger. And then there was that reloader that fired one case 43 times with full loads then claimed the case suffered no serious after effects. All I wanted to know was the weight of the case when he started.

F. Guffey
 
Heavy loads will become difficult to extract because not only are you working the brass but also the steel in the chamber. In a normal load the brass expands and then rebounds when the pressure drops. With over pressure loads the pressure is so much that both the brass and chamber expand a bit. When the steel of the chamber expands and contracts it basically grabs the brass case making it much more difficult to extract the brass. This is why sticky extraction is bad and means your load is too heavy. At least that is my understanding of the subject.
 
You're close, but every single time you fire, the chamber expands elastically. Stress = strain even if it is small. The brass, of course, follows the chamber. In a normal load, the brass does not deform far into the plastic range, if at all. A little plastic deformation is expected, else we would not resize our cases. But too much, and the chamber will have a real grip on the case after the stress is released. FWIW, the chamber expansion is directly related to the resolved stress on the barrel, which is geometrically related to the hydrostatic pressure. The property of the metal that relates elastic strain to stress is a single constant called Young's Modulus.
 
I recommend new reloaders use as much flare as needed to easily seat a bullet, and worry about case "life" later.
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Good advice. And I would even add that it's not just for new loaders. I've been loading for 33 years - to the day, actually (loaded my first round 6/4/84 - and yes, it was a 38 Special); and I flair generously.

I used to belong to that popular school of thought "flair just enough to seat the bullet." But I haven't been in that camp for a long time now. I flair generously. Life is too short to struggle with seating bullets. If I can't just drop the bullet atop the case and it not stay put, I've got some more flairin' to do ;).

When my generous flairing causes shortened case life, I'll let everyone know - I've been waiting for over five years - and counting.
 
What you have just discovered is the same principle that we are trying to achieve in annealing.

Ie. keep the brass in its elastic profile and not its plastic (elastic wants to go back, plastic gives way and stays there).

You got good brass!
 
It's the same reason springs eventually take a set; the metal changes toward the stressed shape in that case because the spring is constraint to its position, but with stress and no constraint there is shifting over time.
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I am going to do a rare if not unheard of disagreement with Unclenick , on just this aspect.

Generally the part about springs taking a set is not true. There are aspects of it that they can take a set on first complete compression depending on how they are made and will not fully rebound, but in general, they do not take a set in the sense they won't rebound.

https://survivalblog.com/letter-re-can-firearms-magazin/

There are more technical l sites but this covers it lightly and with a good example (pistol magazine springs being one type that is intended to be fully compressed and stay that way for many years without any impairment in function.
 
Back in 1971, when I started loading for my pistol I used a generous bell on the cases. I also used a heavy crimp as was suggested for the full power (I was loading just under that level) loads of H110. I very quickly found that all that working of the mouth was causing mouth splits. It wasn't necessarily a bad thing because I could trim the cases and use them as 38 special. I found out very quickly that I was going through my nickel plated cases about three times faster than the brass cases but neither was lasting as long as they should.I reduced the amount of bell so a bullet would sit just inside the mouth without starting into the case. Although the nickel cases were still splitting the brass cases seemed to stop. I started buying only brass cases and stayed clear of the plated cases. My bullets are easily seated and my brass seems to be "indestructible".
 
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