Wayner,
I don't think there is any such THING as obturation in a gun with chambers .013 under groove size.
Powder ignites, blows the ball into the barrel, it just glides through the barrel with no resistance. Forcing cone is just a funnel to get the ball going in the right direction.
BP has from 7 to 10,000 Lead Units of Pressure, LUPs, you guys keep saying CUPs, that is for hi-power rifle with smokeless, 40,000 CUP, or PSi and up..
If the ball doesn't have any resistance to movement except inertia, it ain't gonna grow wider to fill the barrel. That means if it doesn't hit a barrel with grooves smaller than it is, and needs to have enough pressure build up behind it to push it through, it ain't gonna get fat enough, from the pressure build up, to obturate.
If you're gonna say, well, pressure builds up in the chamber, well, yeah, it does, but if it mashes at all in the chamber, it can't get any bigger than the chamber. It still hits the forcing cone at .013 under groove size, and will skip down the bore. If it hits the bore at a couple under, you got some resistance, MAYBE you get obturation. Maybe not. I read somewhere that BP has a flame temp of 7000 degrees. If you got that heat slippin' by the ball, more likely you have metal being burned off the OD of the ball than mushin' the ball to fit the grooves.
Where's your accuracy? We're back to smoothbores. Skip that .36 ball down that .44 bbl. Hey, what the hell, I hit the paper?
Quigley could shoot 800 yds. Sheutzen shooters shot for the smallest hole. If you couldn't make 1 hole consistently, you didn't belong there.
Why we gotta settle for 3 inch groups? If it's the best YOU can shoot with a one hole pistol, OK, but if it is the best the pistol CAN shoot, NOT OK.
Cheers,
George