Floral foam. The wet stuff used dry about 3/16th" thick.

I use regular Styrofoam packing popcorn and have been for 30 years. The reason I like it better than the floral foam disc is that it fills the case but is still relatively weightless.  The reason why I like the filled case better is for the ignition uniformity.  If the case is filled the powder is always in the same position from shot to shot.  If the case is not filled but only capped the powder can assume different positions in the case from shot to shot.  If a wad of any type is used floral or otherwise and that wad is pushed down to the powder leaving space between the wad and the bullet base you stand the chance of ringing a chamber especially in vintage rifle with mild steel barrels.  I do at times also use a card wad on top of the Styrofoam filled case but not always but either way I always fill the case.

Many years ago there were several articles about chamber ringing caused by wads. Has this theory been debunked? I shoot old rifles with soft steel barrels so I haven’t used any wads, but would like to.
Mike

A friend of mine had been using kpock over powder in his 32-40 cpa. He recently did a test with and without and without the kpock accuracy was much improved. I use the dark green floral foam over the case mouth on the smaller capacity cases so I don't spill it in the action. I've tried with them without and cannot detect any  difference. 25 years ago many used to use the light blue  "sill sealer"  and it also worked well from what i remember. I think that's Is what everybody was using in their 32miller shorts on the west coast then.

In my opinion chamber ringing occurs when a wad of any type is seated to the powder of a non case filling load leaving a substantial space between the wad and the bullet base.
On ignition the light weight wad accelerates to a very high velocity before it strikes the bullet base. The high velocity impact causes a hydraulic affect of the bullet base obturating outward at the location of the bullet base of a chambered round.  The chamber ringing occurs at the location of the bullet base of a chambered round.  I do feel that it can happen in any modern steel barrel but likely happens more quickly in vintage mild steel barrels.  I am more than slightly embarrassed to say that I speak from experience.

This is gonna sound rather off the wall, but for purposes of constraining the powder in the bottom of the case has anybody ever considered pre-measured "capsules" of powder? Made of flimsy thin paper, cigarette paper soaked in saltpeter for example, as is done when making combustible cartridges for cap-and-ball revolvers that completely combust upon discharge. Dimensioned for a snug fit in the cartridge case and pushed down against the flash hole. I can see where it could work in a straight-walled case, not so well in a tapered or bottlenecked case. I can also see where it would be a royal PIA to make hundreds of them in preparation for a match.

Just a thought, as the morning coffee starts to kick in.

westerner wrote on May 23^rd, 2023 at 12:51am:

With breach seating of the bullet the bullet base is not in the chamber but in the barrel so if any ringing is taking place it is in the barrel not the chamber.  With fixed ammo the bullet base is in the chamber so when ringing occurs case extraction is affected in that as the ringing gets progressively worse extraction of fired cases get progressively more difficult because the case begins to bulge at the ring which in turn causes resistance to extraction. The deeper the ring the greater the resistance to extraction. 

In all the years I have been using Styrofoam wads I have never noted any degradation of accuracy over the long term.  The Styrofoam after being highly compressed from the internal case pressure is expelled from the barrel as dust.  Also something I watched for over the years is would it act as an abrasive while under such pressure but I have never noticed any abnormal barrel ware.  
Wax wads are not a new idea they have been in used for a long tome.  In some of his writing Harvey Donaldson spoke of adding rosin to his wax wads to help keep them in the case neck. I would think that rosin a substance used to add friction would be abrasive but Mr. Donaldson never mentioned any such affect from it.   At one time I was using granulated wax  used in candle making as a filler but I didnt like it as it added too much weight so did affect chamber pressures. It did work good and likely acted as an additional lube.  I like the Styrofoam packing popcorn because its virtually weightless so has little affect on chamber pressure, it fills the case so gives a more uniform powder ignition, and for as long as I have been using it has shown no negative affect, and its free.  I like free !