R'Man;
Based on the assumotion from your illustrations that the three sizes you list as most apt to bridge is that a line of them, if that's the correct term, would be slightly longer than bore dia. On this basis 5 #2s would = .750", about .021" larger than the 12ga bore dia. 6#5s or 4BBs however would stack up to .720" or about .009" less than 12ga bore dia. Am I m issing something here, or are you taking into acount that all the shot won't run to exact size & the possibility of all in one line being oversize.
I would have to get out my book to look it up for details, but I recall Burrard mentioning a barrrel having three distinct ring bulges. The bbl in question was in a test setup for obstructions where weights of various amounts were placed to check for severity of bulge or a burst. These were simple cylindrical weights which were free to move on impact from the charge. I don't recall for sure who had done the testing, but Burrard reported on many tests which were run by some of the major shell makers in England. The bulge nearest the breech, where the weight was initally placed was the largest & each succeding one toward the muzzle was a little smaller. The conclusion reached was that as the barrel was not burst allowing the pressure to escape a sort of wave pressure was set up which would bounce back to the breech, then forward again til it caught up with the charge & caused another bulge though of les in tensity until it finally became too weak to create another bulge.
