The 'Vertical flame front', a phenomenon actually discovered by Vieille, considered to be the inventor of the 1st successful smokeless powder.  Don't put the wad directly on top of the powder, but a bit ahead, so that the powder column slumps a bit, which should eliminate the risk.

I too use floral foam but it is less than 1/8” thick. Pushed down until it cuts and never push it down on top of the powder. I can shoot sub 1” 5 shot groups at 200 yds using this procedure with my 25 Hornet 

Jack

I'm curious, what's the difference between pushing or not pushing the foam down on the powder?

^^^
This is by far and away the best/simplest explanation of chamber ringing I have seen.

You may get away with a wad directly on the powder for a long time, but eventually you quite possibly will end up with a ringed chamber.

Why take chances?

Vall,

Try seating a 32 Miller short into a high wall chamber without a wad.  You will learn some new swear words I bet!

Evidently there is a science to just about everything...




JMH

I would be interested in knowing if anyone has done any testing as to whether or not placing the wad on the powder results in better accuracy. If anyone has done so, please share your results. 

The original 45-70 Carbine cartridges were loaded with a filler wad of some sort, and I have never heard that those cartridges ever had a problem with chamber ringing. So I am wondering if there would be any reason why we could not use a thick floral foam wad that would fill the case from the powder to the mouth? Has anyone tried that?
Joe S

Thanks Dave,
I understand that we are discussing smokeless powder, was not sure the extent to which black powder would react differently, but I have to assume that people are putting the wad on the powder because they get better results, in which case, maybe they would be willing to share the results of their testing. 

I am also curious to know if a column of floral foam would be save to use. 
Just trying to avoid re-inventing the wheel.
Thanks!
Joe

You are obviously an expert in bench shooting!
Thanks!

WE have not said that putting the wad on the powder WLL cause ringing.

WE are in agreement with Charlie Dell that putting a wad on the powder will significantly increase your chances of it happening.

Many have believed that that chance of happening only occurred in the softer older version of steels in antique firearms.

Unfortunately I have seen it occur in the harder steel barrels on modern barrels put on single shot rifles.

Charlie also indicated the risk of it happend was dependent on how you tipped the rifle forward moving the powder forward or if you shot the rifle aimed in an elevated position.

So yes there are other factors that result in the final outcome.
However not putting the wad on the powder ensures the other mutual conditions will never occur to ring your barrel.

This has been a well-understood phenomenon for about 150 years.   No point in debating about it.    Sometimes the resulting high pressure wave is enough to ring the barrel, sometimes it isn’t.

CHRIS

Joe_S:  Charlie Dell did testing with the wad down on the primer and also with the wad slightly elevated over the powder and his testing also included if the powder was fully against the primer shootng uphill or powder dumped forward from tipping the barrel. These other conditons can also contribute to ringing.  Of coarse they are not as much of a contributing factor when the wad is solid against the powder however these conditons were important regarding the occurance of ringing in Charlie's testing. Others who had more direct contact with Charlie would be better able to explain the results of his testing.

When Charlie had a solid powder column with the wad solid against the primer he achieved barrel ringing doing his research.

  Well, Joe S, if you want this testing done, have at it! The rest of us know all we need to.

I think it would be fun to do however I do no have the lathe skills to do it and won’t live long enough to learn it 
I’m 71 and still working full time to make matters worse

At any rate,may all of your shots be centers!
Joe

Charlie Dell made conclusions for the causes of ringed barrels by doing ACTUAL RESEARCH - not based on assumptions of barrels ringed by some other user who may not be aware of what caused it.

Other than the academic interest, I see little value to this type of discussion, in the context of wondering if it's okay to put a wad against the powder.  It is absolutely not okay to do so, we know very definitely that doing so will have a high probability of causing a ring to occur.  Your initial post stated that you were doing this known ring causing practice, and you stated that you were somewhat new to this type of loading/shooting.  It is very good for those that are more experienced to offer cautions to new shooters on unsafe practices, which is what happened in this thread. 

Now, the analysis of why a ring occurs, and trying to figure out the mechanism, that's a pretty valid, although somewhat academic discussion.  In the context of "I know that a probability of ringing a chamber exists by using a wad on the powder, let's explore why that happens".  Not in the context of "I and my friends just started shooting and we're putting a wad on the powder and I haven't rung my chamber, so maybe it's okay to do so and the research to date just isn't good enough."

However, we live in a culture where we allow people to make their own mistakes, and learn from them, if they wish.  We're not going to stop you from putting a wad on your powder, but we're sure going to inform others that you are encouraging to do the same that there are risks to doing so.  It's all right to make your own mistakes or do your own experiments, but it's useful to inform others of the risks, so they can make an informed decision on whether they also want to take risks or do experiments.

This falls under the category of a type III learner.*

*
type I - learns by reading or hearing about others experiences
type 2 - learns by watching others experiences.   
type 3 - Has to go out and pee on the electric fence himself.

From my experiences messing with wads and other various powder placers the problem lies in the quality of steel used to make the barrels. The old French scientist that perfected smokeless back in the day stated a wad over the powder could increase the pressures at the base of the bullet two to to three times so with that thought in mind my loads are kept below 20,000psi in barrels that will withstand 60,000psi when using a wad. That said, no Eye Towel Yan guns, antiques of any kind or barrels made from suspect steels; modern ordinance steels only! Works for me, YMMV.

No, I don't piss on electric fences but have and will continue to straddle one to get to the other side, lol.

Studies of Shock Wave Reflections and Interactions (Paul Vieille Lecture)

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- the primary focus has been investigation of the behaviour of gas dynamic shock waves expanding on Paul Vieille's knowledge.

THX MartiniBelgian for the direction to more info.

problem to be solved in the 17th century.
1 Introduction
Material properties, an equation of state for the material, and conservation equations
for mass, momentum and energy are required for the mathematical description of
the propagation of blast and shock waves. This was not set up at once, but took a
long way over several centuries. The development of the theory of blast and shock
waves is chronologically described in the following sections.
Torsten D¨oge
Dr. Linse Ingenieure GmbH, Karlstr. 46, 80333 Munich, Germany
e-mail: doege@drlinse.de
Norbert Gebbeken
Institute of Engineering Mechanics and Structural Mechanics, University of the Bundeswehr
Munich, Werner-Heisenber-Weg 39, 85577 Neubiberg, Germany
e-mail: norbert.gebbeken@unibw.de
E. Stein (ed.), The History of Theoretical, Material and Computational Mechanics, 249
Lecture Notes in Applied Mathematics and Mechanics 1,
DOI: 10.1007/978-3-642-39905-3_15, c Springer-Verlag Berlin Heidelberg 2014
250 T. D¨oge and N. Gebbeken
The content of this chapter was collected when writing the dissertation [11]. Only
by reading the original literature it becomes clear, what problems had to be solved,
why problems were not solved until a certain time and why some problems were
then independently solved by several persons. The authors of this chapter recommend to everyone to obtain and read the original literature. It is very instructive!
2 The 17th Century
MARIN MERSENNE (1588–1648) measured around 1636 the speed of sound (LENIHAN [34, 35]). He applied two methods. One method was to measure the time from
the arrival of the flash of a canon, which distance was known, until the arrival of
the report of the canon. With this method, he determined the speed of sound to 230
Toisen per second (≈ 448m/s) [34]. The second method was to measure the time
that a sound and its echo took to a wall and back. With this method he determined
approximately 316 m/s [35].
GALILEO GALILEI (1564–1642) wrote already in his 1638 published work Discorsi e dimostrazioni matematiche intorno a due nuove scienze attenenti alla meccanica et i movimenti locali about experiments on air. Thereby, he described an
experiment, with which the density of air can be determined [22, p. 117–118]:

Short version, no.  It is not a requirement,  but can be beneficial for accuracy and fouling.   Even the airspace thing is relative,  not absolute.