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Brent, I know it is done and will continue to be done. I believe there is no part of a shotshell with a conventional wad that approximates dacron or floral foam over a relatively large air space. Even when shotshells use wadding, there is no load that I am familiar with that has a significant air space that a wad accelerates across before it encounters a stationary shot column. I understand some wads have a crush zone that may be largely air, but that is an engineered control feature not a potential air hammer.

I certainly believe that you have consistent, long term, excellent results with those fast powders, but would you use the same loading technique with 5744 in a BPRC? Though it wasn't mentioned, my suspicion is that the goal is to approximate original ballistics with slower smokeless powders that will not fill the types of cases that are probably being considered. If I had to guess, Unique or 4227 may do for reduced loads, but not likely to approximate traditional full power double rifle loads. But, I'm sure there are exceptions that I'm not aware of.

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Originally Posted By: WBLDon
Please excuse my ignorance but what is "backer rod" and where do you get it? I have used dacron for years without an issue.


Backer rod is used for filling up space you are going to caulk. You can find it at hardware stores in different size diameters.

Ken

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Thank You Ken!

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justin Offline OP
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BPCR?

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Black Powder Cartridge Rifle

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justin Offline OP
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Thank you Rem.,
So, if the use of Dacron can lead to ringing the barrel what about the backing rod?

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A shotgun shell is solidly filled from the powder to the shot like a rifle case full of COW from powder to bullet. It's the powder surface parallel to and spaced from the bullet's base that acts like a shaped charge and a wall of high pressure meets the bullet's base and acts sideways to form the ring. Unfortunately it is more likely to happen in old barrel steels which may be on valuable rifles. I have not found any need to use a filler in any of my large capacity (relative to the amount of powder being used) cases. If you are using any wad on top of the powder and spaced from the bullet please stop at the first sign of a case resisting extraction. The ring will form where the base of the bullet sits and will progressively get worse.

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Found this in a previous discussion:
Major Sir Gerald Burrard in the second edition of The Modern Shotgun (1948), Volume 3, The Gun and The Cartridge, “The Diagnosis of a Burst” discussed “Wave” Pressures and the etiology of multiple bulges pp. 364-375.
p. 365
When the explosive charge was placed entirely at one end of the closed vessel (discussing experiments by Paul Marie Eugène Vieille and published in Etude des Pressions Ondulatoires in 1890) the gases given off naturally rushed forwards along the length of the vessel until the forward layer of gases was suddenly checked by the closed end. When this occurred the gases which were behind the extreme forward layer over-took this layer and began to pile up against it, with the result that the extreme forward layer was compressed with great violence. It was this compression of the extreme forward layer of gases which caused the high pressure…
p. 368
Since this wave pressure acts radially outwards the wall of the barrel is submitted to a very severe pressure all round its circumference, and if the pressure is sufficient to stress the barrel beyond the elastic limit of the steel a permanent bulge all round the bore is the result. Such a bulge is knows as a “Ring Bulge” …

Note that if the surface of the powder is not perpendicular to the run to the bullet then the shaped charge effect is broken up by the random nature of the pressure "walls" formed off the uneven surface. Also note that Dell was able to ring a barrel with no wads at all involved merely by shooting straight up thus starting with a level surface on the powder.

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Justin,

Placing anything in the case CAN result in chamber ringing. It doesn't matter what it is. The problems with Dacron (or anything else) arise when people place a small amount in the case to hold the charge back with airspace between the filler and the bullet. When the powder is ignited the filler is propelled into the stationary bullet which acts like an obstruction and the filler is forced to move outwards causing the ring. If you choose to use filler (and there are situations where you have to) you MUST completely fill the air space in the case with the filler. Doing it this way results in a progressive amount of force being placed on the bullet as the filler moves forward. This eliminates the problem of the filler gaining momentum and then impacting the bullet which causes the ring.

What exactly are you loading for? If you're loading for a single barrel rifle you have more options than if you're loading for a double as you don't need to worry about regulation. Many black powder cartridges can be loaded with 5744 or Trailboss with no filler needed. If you are loading for a double though you may not get it to regulate with those. If loading nitro for black (NFB) loads in a double, IMR or H4198 with filler is a standard loading that's used by many many people (including myself) with no issues in rifles that cost more than most cars to replace if damaged.
If you're loading full nitro loads in a double rifle you can usually use IMR or H4831 without filler. There are exceptions though and the 450 and 475 3 1/2" Nitro come to mind. There is just to much space to get reliable ignition without a filler. Even when you can get away without a filler many choose to use RL15 and a filler as it results in less perceived recoil. This is not something only done by a few, it's common in the world of nitro double rifles. It's the way Kynoch chose to go when they reintroduced nitro express ammunition. They even sold cut up backer rod for others to use in reloading.
The internet is a wonderful place to get info but you need to be wary of where it comes from when everyone has a voice. It's worse when you don't ask a specific enough question and others speculate.

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justin Offline OP
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So, the ringing potential can be mitigated by filling up the cartridge with Dacron,over the powder,to the very top and then inserting the bullet?
Does the backing rod melt away before the pressure hits the bullet thus negating it's taking up all the space between powder and bullet?
Anyways,I'm shooting an old black powder double. Late Victorian age. I use the IMR 4198 powder and a hornaday 300grain bullet.

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