Rat: Yes, the pressures drop off rapidly as one measures them towards the muzzle. How rapidly? I have no information.
What are the breech pressure in a .54? Here again I have no real information, but I like you have heard of pressures in the 20,000+ PSI range with some blackpowder loads.
Putting all of this speculation together I chose 15,000 PSI as a possible maximum pressure, thinking that if someone put a 160 grain powder load under a 444 grain POWERBELT(tm) .54 caliber bullet the guess might not be too far off base. (I've read of folks who have what I call the BlackPowderMagnum syndrome who might think this is a neat load).
Anyway, when it comes to things that can blow my head off if I'm wrong, I choose to be on the safe side.
If it wasn't a lot of work, and if I wasn't up to my arse in snapping turtles I would build a model with a .75 barrel complete with dovetail sight, BUT, I really don't have the time.
Please don't take this personally, but if I did find the time, someone would ask the legitimate question you asked about the pressures I used in the analysis, and I couldn't defend them any better than I did here so, I'll just stick to my guns and say "I wouldn't build a .54 cal rifled gun with a .75 inch octagon barrel muzzle. Especially with a dovetailed front sight on it."
For the record, I did all my model building and analysis on my lunch break. :: :: :: :crackup: :crackup: :winking:
What are the breech pressure in a .54? Here again I have no real information, but I like you have heard of pressures in the 20,000+ PSI range with some blackpowder loads.
Putting all of this speculation together I chose 15,000 PSI as a possible maximum pressure, thinking that if someone put a 160 grain powder load under a 444 grain POWERBELT(tm) .54 caliber bullet the guess might not be too far off base. (I've read of folks who have what I call the BlackPowderMagnum syndrome who might think this is a neat load).
Anyway, when it comes to things that can blow my head off if I'm wrong, I choose to be on the safe side.
If it wasn't a lot of work, and if I wasn't up to my arse in snapping turtles I would build a model with a .75 barrel complete with dovetail sight, BUT, I really don't have the time.
Please don't take this personally, but if I did find the time, someone would ask the legitimate question you asked about the pressures I used in the analysis, and I couldn't defend them any better than I did here so, I'll just stick to my guns and say "I wouldn't build a .54 cal rifled gun with a .75 inch octagon barrel muzzle. Especially with a dovetailed front sight on it."
For the record, I did all my model building and analysis on my lunch break. :: :: :: :crackup: :crackup: :winking: