WBLDon, you must be lucky. Charlie Dell in his Modern Schuetzen Rifle performed extensive testing on chamber ringing. This ringing had first been noted by the Frenchman who had developed smokeless powder and was reported later by Major Sir Gerrald Burrard in British shotgun chambers. In Dell's testing he found he could ring a chamber at will using dacron holding the powder to the rear of the case. The ring would form gradually at the base of the bullet. Depending on the quality of the barrel steel it might take 6 to 30 shots to form to the point that it was hard to remove the case from the chamber. He also did it using a thin cork wad on the powder. A thin cork wad off the powder by .20 or so did less damage but was still a factor. Kapok seemed to cause less problems than dacron. At one point he even discovered that he could ring the chamber with no filler/wad at all just by shooting straight up. The problem was that a high intensity pressure wave formed on a level surface of powder and propagated to the base of the bullet. The same powder spread out in the case was no problem. A full case of powder was no problem and a case completely filled with something like cream of wheat or corn meal over the powder was also no problem.