Dwell Time When Sizing -- Any Actual Basis in Fact??

[Dusty Stevens]

where is Guffey he should have been all over this, maybe he be doing the Bump

oh he's busy right now

 

[dsculley]

From my perspective, Riflewoman provided the most intelligent/informed answer. Dwell time could possibly reduce spring back but common sense says that would require more than a few seconds dwell time since we are talking thousandths of an inch. If brass is properly annealed I don't see any advantage.

It is humorous to me that so many people talk about the science of reloading and doing proper research but when an industry professional speaks they are dismissed so handily.

 

[BoydAllen]

Qualifying this a concerning used brass that has not been annealed after it was manufactured, there are two kind of folks here, those that have done the experiment with the aforementioned brass, and those that have not. I have. Have you? Has she? The common pitfall with simply using some general principle is that the problem may have been incorrectly understood. Testing is the best way to eliminate this potential pitfall.

 

[fguffey]

It is humorous to me that so many people talk about the science of reloading and doing proper research but when an industry professional speaks they are dismissed so handily.

I have said reloaders are threatened when the science of reloading and proper research is discussed. I have suggested the reloader determine if the case has more resistance to sizing than the press can overcome; about the only feed back I get is 'DUH?'

I have suggested the reloader use a feeler gage to determine the gap between the top of the shell holder and bottom of the die, if the reloader had had time they could measure the gap and then wait 10 seconds and measure the gap again. And then someone would have to explain to the reloader when adjusting the die in a cam over press is different than when adjusting a die in a non cam over press.

There are methods and or techniques that can be used to increase the presses ability to overcome the cases ability to resist sizing. And there are ways to determine if the die and shell holder has the ability to return the case to minimum length/size.

F. Guffey

 

[fguffey]

That means the cases are formed in stages but the total time in a die is about half a second. From straight cylinder to tapered and necked case is only 4 or 5 stages. If there was any significance to the “dwell” theory, then the presses would have to run much slower.

And in the process of all that dwelling the case is annealed at least 4 times if not more.

I found a deal at an iron & metal salvage yard. The deal involved 30/06 cases, I thought they were magnificent cases. I processed 40 of them and stated shooting them, on the second round of firing the 40 cases I was told there was a mistake made at an arsenal; seems they were trying to save time/money so they eliminated one annealing process thinking it was not necessary.

I did not need the cases and to add the cases to the collectable drawer meant I would not miss them. I have added to the collection. I cleaned out the shop of an old friend/smith/professor, when sorting through his components I found 80 cases that he had fired. He was not in the habit of shooting reduced loads. My opinion of the cases did not change, I still believe the cases were magnificent cases.

F. Guffey

 

[dmoran]

Like so many aspects in reloading, the correct answers are individual to ones own circumstances -IMO.
Effecting variations of dwell time:

Brands:: Lapua, verses Norma, verses Hornady, verses Federal..... Will they all respond the same?
Shoulder angles:: 23, verses 30, verses 35, verses 40..... How much response indifference?
Wall thickness:: .014" verses .016" verses .018" verses .020"..... Will they all respond the same?
Dies used:: expander ball, verses bushing, verses collet.... How does each effect dwell time?
Cartridge size:: 223, verses 243, verses 284, verses 300.... Will they all respond the same?
Hardness:: new, verses once fired, verses annealed, verses cycled... How equal will they respond?
What level of measurement:: to .001", or to .0005", or to .00005", or more?
And so on.....​

From which one persons input to there own scenario's, likely may differ from another's input to how there cases respond to press operations. As I wrote in Reply #15: "My own results are what I care about..."
Donovan

 

[ebb]

FGuffey in post number 44 the middle paragraph made a lot of sense to me I will try the feller gauge next time I size brass. I have also read post 45 and have no idea what you are trying to say and Ive read it several times. I wish you could communicate better you may have something to say.

 

[fguffey]

And in the process of all that dwelling the case is annealed at least 4 times if not more.

ebb,, most of this stuff is not for everyone, you had no problem understanding the part about dwell time during the manufacturing of the case.

F. Guffey

 

[dmoran]

ebb,, most of this stuff is not for everyone...

Agree 100%... most of your stuff is for you only. As you so often say: you are the only one !.!.!

 

[Sheldon N]

I do a lot of resizing rifle cases on a Dillon 550. When I'm in a hurry I crank through the press cycle pretty fast, size/advance/size/advance nonstop. I've seen that I do get about a half thou more shoulder bump on average if I slow down and do a full hard stop with rest at the bottom of the press stroke.

Now is there a difference between 1 second and 3 seconds dwell time? Not sure about that.

Other big factor I notice is case lube. First two or three cases through the die seem to get slightly less shoulder bump than after the die gets freshly/thoroughly lubricated. This can be between a half thou and a full thou. I'm using the alcohol/lanolin mix lube.

 

[ClassCat]

I do a lot of resizing rifle cases on a Dillon 550. When I'm in a hurry I crank through the press cycle pretty fast, size/advance/size/advance nonstop. I've seen that I do get about a half thou more shoulder bump on average if I slow down and do a full hard stop with rest at the bottom of the press stroke.

Now is there a difference between 1 second and 3 seconds dwell time? Not sure about that.

Other big factor I notice is case lube. First two or three cases through the die seem to get slightly less shoulder bump than after the die gets freshly/thoroughly lubricated. This can be between a half thou and a full thou. I'm using the alcohol/lanolin mix lube.

Dillon's case lube. Pretty good for mass production. Make sure you get that slime off the cases before you fire them.

 

[Sheldon N]

Dillon's case lube. Pretty good for mass production. Make sure you get that slime off the cases before you fire them.

Dillon case lube is the same as the homemade stuff that I'm using, just a mixture of 99% alcohol and lanolin in a ~10:1 ratio. It's great. Yes, I tumble the brass afterward to get it clean.

 

[6MMsteve]

Guffey knows when the vittles r a cookin

 

[alinwa]

No you are wrong which is typical for someone with an opinion that is not based on real experience.
Measurement to the nearest .0001" is far more accurate than your sense of touch. I do not have a means to measure with that accuracy but if I did I would sure use it.
Even so measurement to .001 is a real number that is quantifiable.
Measurement to touch does nit mean as much since touch from one person to the next is highly variable.
Like I said you can make it work or not depending on your personal agenda.

BTW gauging or gaging has different meanings. What do you call the use of a Hornady Lock and Load Case Gage? Gaging of course....

L-O-freaky-NELL!!!


Sentence by Sentence ya's just can't make this hole any deeper if ya's tried!

OK, OK, I'll just refrain...... measure away my man, measure away

 

[Dusty Stevens]

L-O-freaky-NELL!!!


Sentence by Sentence ya's just can't make this hole any deeper if ya's tried!

OK, OK, I'll just refrain...... measure away my man, measure away

Those frankford arsenal calipers measure to the .0001 Al. Ive seen losts of posts about them.

 

[Howland]

As a doubting Thomas you would not believe anything we say either way.
If you do not have a highly accurate and consistent way to measure shoulder location there is no way for you to learn or be convinced or what the real facts are. The tool I use is a Stoney Point case gage now sold as the Hornady Lock and Load Case Gage. With my calipers it appears to repeat to .001".

It is easiest to understand this concept when forming cases. Some of these guys will have indeterminate or no results because they try to speak while only bumping shoulders of work hardened cases back about 1 or 2 thousandths. You also cannot just size 2 or 3 cases and get an accurate understanding either.

You also need to be honest with your own opinions and agenda. After working on process tooling, set up and development in manufacturing for more than 40 years I have seen many cases where personnel make a process fail because they don't like the process or that it was not their idea. That is just humans being contrary.

I first studied this phenomenon in detail nearly 20 years ago after getting the Stoney Point tool. I formed 100 new Hornady Frontier .303 Brit cases to 6.5X53R Dutch Mannlicher. My initial goal was 100% yield. With the cost of new brass so high and so limited in availability I had no interest in scrapping any or buying more.

I stripped the Mannlicher bolt to obtain the best feel of case fit.
I started developing the process using older cases that had been fired a variety of times. I initially tried to form the cases in one pass which resulted in accordioned shoulders except with a few FC cases.
The process that worked easily used 3 intermediate dies before the final sizing with a trim die. During process development I ruined about 15 old cases before I got all good ones. Then I switched to forming the new cases.
As I found the exact die setting on the trim die I checked the case shoulder position repeatedly as I snuck up on the exact feel I wanted in the rifle. Not every case reacted the same way to the final forming stroke. I has cases vary and because I measured each one immediately I began to notice variations in shoulder position corresponded to the force I had to apply to the press handle. All of the following affected the shoulder position:
1. More or less lube
2. Faster or slower sizing strokes
3. More dwell , less dwell or no dwell at the top of the stroke.
4. Multiple sizing strokes at the same setting vs one stroke. You might say more strokes vs fewer strokes.

I was working with new brass and you might assume that it was all the same.state of anneal. But you have to assume fired cases with different work hardening states will cause variations too.

When forming these cases a fast sizing stroke gave a longer case.
Too little lube gave a longer case. No dwell gave a longer case. One stroke gave a longer case than 2, 3 or 4 strokes. Beyond about 3 or 4 strokes the cases never got any shorter.

There is always the possibility of variation if your sizing technique dies not form the case shoulder to the fullest extent of your die setting. To consistently get the full sizing permitted by your die setting you need the following:
1. Uniform lube
2. Slow steady sizing strokes
3. About 3 to 4 seconds dwell at the top of each stroke. It really does take time for the brass to creep to its final position.
4. After the first stroke retract the case about 1/2" turn the case 120 degrees. Slowly size again with the dwell. Then retract and turn the case another 120 degrees. Then size again with dwell. Now check the case length from the head to the shoulder. It should be exactly the same as all other cases sized with the same technique.
If this seems like a lot of busy work you have to ask yourself if you want it fast or if you want it right. You do not get both at the same time if your calipers are honest.
It takes very little difference in technique to make the process vary by .002". Over the 100 formed cases mentioned I measured each one and checked the fit in the chamber 100% as each case was formed. When I got a case that was .001 to .002 longer it always corresponded to something that accidentally varied. Those longer cases were sized again until they matched the rest. As I learned what caused the longer cases I changed my technique and the variations went away.
I learned that lube, speed of the sizing strokes, multiple strokes and dwell time could all contribute to a much more exact and robust sizing process.

If you test enough cases you can reach your own conclusions.

This answers the question OP asked. The reason he asked is to avoid having to reinvent the wheel if someone here has already crossed that bridge.

That is exactly why I visit this site, to avail myself of the knowledge those with more experience than myself are willing to share.

Having a fair amount of reloading experience but just getting into full length sizing for long range precision with bottleneck rifle, minimizing variability in setting the shoulder gets me closer to my objective.

Thanks @ireload2.

 

[CharlieNC]

This is one of those issues which is fast and simple for anyone to determine themselves using a comparator. Regardless of theory, there are enough loaders who proved to themselves (including me) that dwell time and/or multiple passes can make a significant difference, not necessarily 100% of the time but enough it should not be ignored. Main problem is the OP does not own a comparator and wondering; its an indespensible tool.,

 

[suasponte]

Yes, Dwell time does make a difference on brass sizing.

 

[Damon555]

Statistically speaking if the results are lower than the margin of error (of which there is no mention) the outcome is meaningless. Perceived or not. I'd like to see quantifiable evidence derived from a test using the scientific method to prove that gains made in the concentricity of reloaded ammunition by dwelling in the die have any real effect when the bullet hits the target. I don't see any information out there that actually proves that dwell time works by overcoming some margin of error however large or small.

The more free time that people have it seems the more tedious they are willing to make their reloading process.

 

[Bart B.]

the ammo company presses operate at about 50 strokes per minute. That means the cases are formed in stages but the total time in a die is about half a second. From straight cylinder to tapered and necked case is only 4 or 5 stages.

How much time does a stamped cartridge brass coin spend in cup and draw dies before its head and primer pocket are completely formed with rimming, bunting and punching dies, then it's straight cylinder body is tapered, shouldered and neck trimmed?

The case forming machines I've seen at Lake City arsenal, Hornady and Starline seem to have a given case spend much more time in all dies adding up to much more than half a second.