Well, I finally got the article read. I have some real problems with what was written, IF I understand the author to be saying all faster burning powders may be a problem. I understand and agree with fillers and wads possibly creating some pressure problems, but I'm not sure the author was limiting his article to that situation.
Now, why do I have a problem with a prohibition on using small amounts of fast burning powder or, putting it another way, having empty case space?
(1) Not all loads completely fill a particular case. I recently loaded some 7mm Mags with 68.0 gr of IMR 4350 and 139 gr Hornady JSPs at 3250 fps. That's a pretty hot load by today's standards and yet, there is empty case space. You can shake the case and hear powder moving like it belongs in a mariachi band!.
(2) Large pistol cases have used 25% of capacity or less for load densities for years without problems. Even the .357 Mag has less than 25% load density when it is loaded with 3.0 gr of Bullseye and a 148 gr LWC. Alliant shows a Green Dot load of 2.8 gr, but the case will hold 12.6 gr of Green Dot. That's 22% of the case capacity.
(3) Pressure doesn't just peak at one point in a case, unless there is an obstruction of some sort, besides the bullet. If it did, the new piezo transducer measurement of pressure would be meaningless, just as the copper crusher would be. Of course, if there is an obstruction, like a wad or filler, the case is reduced by the thickness of the materials and can create excess pressure where the material is located. This is especially true if you consider the filler/wad is compressing, instead of moving the bullet, and the pressure is building all that time.
(4) The physical shape of the powder has something to do with its ability to ignite easily and completely. Even though two powders have roughly the same burning rate, one may be easier to ignite than the other. A flake powder, like Blue Dot, Green Dot and etc., is easier to ignite than a ball powder, like 231. That's the main reason magnum primers are recommended when using ball powders. Even with the same burning rate, there may be a difference in length of time and pressure spike from ignition to complete burn out
(5) It has been a standard practice for many to use 700X or Bullseye in the 7.0-10.0 gr range to fireform bottle necked cases. I haven't ever heard of chamber ringing from that practice and you know that's far from a max load.
(6) Some powders need a certain amount of pressure to perform properly. 2400 seems to be one that likes a higher degree of pressure to burn properly.
(7) 12.0 gr Green Dot with a 405 gr bullet doesn't compare too badly with a 7/8 ounce (382.8 gr) 20 gauge with 11.2 gr of Green Dot (velocity is 1050 fps for it and the .45/70).
Of course, I could be wrong on all of this, but there sure seems to be many more factors involved than what was presented. The main concern I have with less than 50% of case capacity loads is the possibility of double loads. Therefore, I never let the case leave my hand, from the time I put powder in it until it has a bullet seated.
