Time between sizing and seating; Does it have an effect?

[BoydAllen]

I can assure you that you are incorrect, and further recommend that you do some testing, since your conclusion is based on absolutely no data. Lots of us have experience with this situation. We have drawn our conclusions after actually doing things, and measuring the results. Evidently you have not.

 

[lynn]

Ouch
Sounds like somebody woke up on the wrongside of the bed this morning.
I take it that dissimilar metals such as brass and copper with wet moisture from the air never corrode then given a 2 month wait?
Lynn

 

[BoydAllen]

Lynn,
I expect that long range shooters, or anyone else who preloads, may not have come across this, but it is not corrosion. Fresno's climate, in the summer is anything but damp, and as you may know, air conditioning reduces humidity. My objection is that when actual experience over an extended period of time has been offered, that someone would contradict it having apparently only "thought" about it. Give me a break.
Boyd

 

[MGYSGT]

Well then, if springback continues for a period of time after sizing. Would annealing after sizing or swagging, or before for that matter, stop this springback in its tracks?

I see someone posted a difference of 40 lbs of seating pressure. Seems like a lot. Would you be able to measure this springback in .001 if you tried?


Tom

 

[philip140]

Hi guys, this is a real interesting subject and something that has played on my mind for some time. I don't know if anybody has mentioned this but has anybody heard of this happening to factory loaded ammo? i.e. fresh from the factory vs a few years old. I haven't.

When reloading the other day I was full length sizing my Winchester brass (.243) that has previously been fired, I noticed that in my box of reloading goodies I had brass from the same batch that had been FL sized 6 or more months ago, so I ran those through the FL sizer again just for the hell of it incase time had changed anything. When all was said and done and it was time to seat the bullets, the brass that had been FL sized months ago (and again only minutes ago) still needed 2x more pressure to seat. Both sets of brass had been annealed prior to FL sizing.
My thinking is that it could be oxidizing of the inside of the case mouth, but saying that I did clean the inside of all case mouths prior to seating bullets.

Phil (still none the wiser)

 

[bsoutlaw32]

If its caused by springback you should be able to measure it with a good quailty caliper or high quality plug gauge set! I will size a few tonight and plug guage it then watch them over the next month and see what happens!

Are we saying then if we FL a case that fits tight into a chamber and come back 2 months later it will be tigher fitting in the chamber because of springback?

How can a bullet seat tighter after 2 months when you only use a bushing die with no expander ball? would it not springback outward not inward?

 

[BoydAllen]

I think that we need to find another descriptive term for this other than spring back. Normally, I use the term to describe the difference between chamber neck diameter, and that of a case fired in it, or perhaps the difference between the ID of a sizing bushing and the diameter of a case neck that was sized with it. In both examples, the dimensional difference is immediate. What I and others have described may not even show as a proportional dimensional change, which is why I have have a working theory that looks at the grain boundaries of the alloy. My investigation of this is far from complete. I encourage anyone else, who is interested, to do their own experiments, and hopefully share the results. One question for the metallurgists out there.. does brass that has been worked, continue to harden over time?

 

[Nodak7mm]

Boyd,

You sure are one moody kinda cat, one post your pi$$y, the next helpful and full of info. I post a basic question, you tell me to go conduct a test. Another guy ponders a thought out loud and you tell him his conclusion is wrong and he did not conclude anything..

No one is contridicting your conclusions or contesting your experience, so c'mon, play nice and let whoever wants to chime in with their ideas, theories, hypothesis, & smoke and mirrors, let em go.. Your tone in several of your posts has you coming across all mad at the world... Chill my friend and share some of that California Sunshine, I know ya can do it.. ;D

I want to hear voices of experiences like yours & the fresh ideas of others to chime in.

Rod Vigstol in Fargo

 

[BoydAllen]

Fair enough. When you're right, you're right.
Boyd

 

[mikecr]

There are atleast a couple factors in this discussion that are amiss from the git go.
#1 Tension(bullet grip) IS springback, and NOT seating force.
#2 With sizing, energy is added in a direction and is not lost(relieved over time) in that same direction.

#1 Notions that higher seating force means higher tension fail tests. Your tension amounts to the springback force gripping the bullet, and that's it. You can undersize a neck till it damages noses to seat bullets in it, and there is absolutely no further grip on that bullet than normal sizing provides.
You're just adding excess(evil) energy there for nothing.

#2 When you add energy, some is lost immediately, some over time, until the added energy -vs- the brass's own inherent energy is again in balance. In other words, your energy is counter to the brass's energy.
When you expand a neck and it immediately springs back, it isn't fully in balance yet. The brass still has more energy left to counter yours with. I don't know why the time delay, but it's there to accept for now. So to the question of 'would tension rise with continuing springback?',, yes it would. More brass energy is still there.
And regardless of your sizing method, expansion was the last energy added(with bullet seating), so the variable left is only inherent springback(freely independent of your energy) to counter.

There is no reason to think this is an action to observe -only in neck sizing. Shoulder bumps, body bumps, and primer seating follow suit.
Don't believe me? Like Boyd said, measure it yourself.

Annealing(actually stress relieving) takes inherent energy away from brass. It's stored countering energy(or life).
But don't forget that you put that energy there by cycling brass dimensions(changing it's grain). And to manage a result, you might instead manage it's cause.

 

[BoydAllen]

Mikecr,
If I may, there is one thing that bullet pull tests do not measure, that I believe can be significant. When we go to a smaller bushing, the step in the neck at the heel of the bullet (talkin' flat base here) becomes larger, with the result (I think) that that the maximum distance that a bullet can be pushed into the rifling is increased. Furthermore, I believe that this increase in engagement increases the amount of pressure needed to start the bullet down the bore. There are several assumptions in this that I would never present as proven fact. What do you think?
Boyd

 

[Forum Boss]

In a previous discussion of this subject, one gentleman who was a plumber in real life observed that copper tubing definitely became 'stiffer' and less malleable/bendable with time. He said he could observe this on un-used tubing that hung on the walls of his shop. This may be due to oxidation. It may be due to other factors.

As Boyd noticed, it's not so much that the ID of the brass retracts (gets smaller) over time, but that the brass, as it ages, has less "give". This brings us to another discussion -- we all tend to describe "neck tension" by diametrical measurements, namely the difference between sized neck diameter and loaded round OD. In fact, there is more going on. Neck tension is affected by BOTH the difference in diameters (dimensional grip) and the case-neck metal's degree of resistance to expansion. This is easy to imagine if you think of cases made of different substances, all with the same neck ID (interior diameter). One case is made of rubber, one brass, one steel. They can all have the same ID, but the steel case will resist expansion much more than the brass, while the "rubber neck" may resist expansion only minimally.

What folks are observing is that brass becomes harder/stiffer with time. That's why we really need to modify our definition of "neck tension". The nominal caseneck ID/OD are only part of the story. I'm not a metallurgist so I can't explain exactly what is going only, but I suspect it is a combination of oxidation of the surface layers combined with a slow, gradual change of the internal structure of the brass by which it becomes less malleable and requires more force to expand.

 

[necchi]

Thank you mikecr,
Had to read that a few times for it to sink in, but the bulb came on.

And Thank you Boss,
It's great to be reminded of old lessons.

 

[swt5]

Please help the new guy understand; you fire a round, the brass expands against the chamber walls then almost immediately "springs back" a bit or you'd have stuck cases all the time...I think I got that. Then you resize the neck and an expander ball or mandrel pushes the brass outward and again, the brass wants to "spring back" and continues to do so over time...I think I got that too. Does "spring back" happen the other way too? ie: I use a neck sizing collet die so the neck ID is not resized to sub caliber dimensions thus there is no finishing step of an expander ball? Does the brass "spring back" to less neck tension over time?

 

[Nodak7mm]

Wow! There sure have been some thought provoking posts which are causing some cerebral cortex meltdown, yet making sense.

I definitely concur with MikeCR's statement post regarding "Neck Tension" and that is not proportinatly equal seating force, therefore the measured force is takes to seat a bullet is not the retained grip strength. This I dont know how we could measure this without having the capability of embedding a strain gage of sorts in the surface of the bullet.. (yeah right...lol)

But we as reloaders and considering the standard tooling we have, we tend to use the term neck tension tied to the bushing dia we used to size the case. Its the only reference we can attach to that act to describe to another reloader what we did. So yes, it is not an accurate statement, but its all we have...

Springback, hmmmm.... To me, springback is the action/force a metal goes thru attemping to return to its state of production. But even then reaching that production point, it seeks to return to its "orig" state. can that be measured? Sure as heck not by me.. Thats getting into the molecular level that is way beyond anything I can control. Like Forum boss mentioned, each metal/material has its own properties of growth, resistance, tensile propertiess, malablility, etc..

But how can we as reloaders measure that? The only way we can and that is squeeze it to a known dia and measure after it. But, is that accurate? Heck no, but it is all we have at our level of "lab sophistication".. And we need something to establish our "base parameters"

There are many factors that can affect springback and time is certainly one of them. I dont know much about brass and copper, but I used to work alot with aluminum alloys and recall that there are various states & purities of alloys that had "shelf life" to them, if they sat too long before a hardening/working/treating (whatever) process, we couldnt use it because it aged. Change at the molecular levels.

Oh crap, now all some of the various aspects of metal fatigue, damage tolorence analysis, cyclic fatigue, crystiline realignment and such black magic is starting to come back to me.... Reloading is spose to be fun... Lol!

Great topic, great thoughts and great people! Dang I love this site.....

BSoutlaw... I sure heck will be bugging you to find out the results of your experiment with the plug gages.. And I do have my 600 yard load dialed. It was my embarrasing performance at 300 that was causing me grief. I hope to give you a run for your money next saturday..... ;D

My brain hurts and I am not so sure I really added any valid substance to the topic, but it felt good to think out loud..

Rod

 

[lynn]

Nodak
Don't worry aboutBod we have a little bit of history and nothing he says is taken seriously.

Boyd
Us longrange guys pre-load while others like Cheechako load at the range so nothing new there.
I also own a pair of 50BMG's were surplus ammo is commonly 50 years old or older.When pulling bullets out of 65 year old brass properly stored it pulls remarkably similar to brass that has been loaded that very same day while rounds left in the truck for a couple of months tend to pull harder.Am I too conclude my trucjk is at fault?
I also load alot of 6mm-06 brass out of Lapua 30-06 brass.
I neck it down and seat a bullet and so far none of my bullets have fallen into the case after the brass sprungback after a six month wait.I guess springback is one directional?
It doesn't matter what your humidity is in Fresno as fired rounds produce water and not all of it leaves the barrel.
Lynn

 

[Nodak7mm]

Nodak
Don't worry aboutBod we have a little bit of history and nothing he says is taken seriously.

Certainly none taken.. I think he is a great guy for coming back on the post and saying "Fair enough"!! That was kool... He seemed/sounded kinda testy and I was feeling like like my normal smart aleck, yet respectful self and couldnt help but tease him a bit about being testy. Hell he has a lot more experience at this game then I do. I'm a gonna listen to what he says, for the most part.... ;D Hell I dont take myself seriously.....

Rod

 

[BoydAllen]

Lynn,
Perhaps you didn't look carefully enough at what I wrote, since none of your examples refer to the same thing that I described. To review, if I size some PPC cases and don't load them till a few weeks later, and compare the force required to seat bullet in those cases (using an arbor press, which is much more sensitive) to the force required to seat bullets in cases from the same lot, that have been fired and sized the same number of times, but were sized just before loading (including seating bullets), the cases that were sized a couple of weeks earlier take more force to seat the bullet than the ones that were sized just before seating. I am not the only one that has reported this. Others have discussed it as well. I did not attribute this to spring back, that was in someone else's post. My theory is that the grain boundries in the brass are temporarily slightly weakened by the sizing of the case, and may slowly return to their former condition over time, after which there is more resistance to deformation that occurs as a bullet is seated. It is not that I am above having my theories criticized, it is that I would prefer that the criticisms refer to what I have actually written. I also mentioned that if I expand necks in a way that gives a perfect fit when turning is done immediately, that the fit becomes too tight if I wait a couple of days to turn, requiring another pass of the expander to restore the fit. None of this has anything to do with the examples that you cited.
Boyd

 

[sailhertoo]

Please help the new guy understand; you fire a round, the brass expands against the chamber walls then almost immediately "springs back" a bit or you'd have stuck cases all the time...I think I got that. Then you resize the neck and an expander ball or mandrel pushes the brass outward and again, the brass wants to "spring back" and continues to do so over time...I think I got that too. Does "spring back" happen the other way too? ie: I use a neck sizing collet die so the neck ID is not resized to sub caliber dimensions thus there is no finishing step of an expander ball? Does the brass "spring back" to less neck tension over time?

This here is a good question. What if you don't use a expander ball and just size the neck with a bushing? Will it tend to spring outward giving less neck tension?

 

[lynn]

The reason I posted about my 6mm-06 rounds is they are only sized down on the necks and don't get looser over time they get tighter.
This would tend to show it isn't brass springback as springback would mean they are opening back up to there original size(30 cal).

Boyd
I did read what you wrote.
Lynn