James-l: I'm no expert, or suggesting you're wrong in your essential point, but as I understand it, BP does burn it's way much farther up the pipe than smokeless (a longer explosion in both time and distance), creating somewhat different pressures at different points in the barrel. Others who understand much better will no doubt weigh in on this. TT

"The very acme of duck shooting is a big 10, taking ducks in pass shooting only." - Charles Askins