Max powder charge in a GM 7/8" barrel (.50)

[Norseman]

What is the MAX charge in a Green mountain 7/8" X 42" in .50 cal (RB)?  How about the best hunting loads and target loads/patch combinations you all have come up with using FFF or FF using this barrel on your rifle.  My rifle will be a flint by the way.  It's being built now and I would like to get some ideas.  I am used to the Lyman GP rifle in .54 (percussion) had it for 13 years.  It's Max charge according to LYMAN is 100 grains of FF, and 80 Grains of FFF.  I would appreciate your inputs/insight on this!  My GP's most accurate is a .530 with 80 grains of FF using a TC .018 pillow ticking.  How about the 7/8" GM in .50?

[BS]

This was posted on americanlongrifles.com:

"Maybe you guys were waiting for me to chime in. A 7/8" 50 cal. barrel has always been a nice weight barrel to build a gun with. As
for its "safety", let me say this. We occassionally build a 50 cal.
barrel in 13/16" size. After proofing these with 300 grains of FFF,
with two patched balls, we felt it was a "safe" barrel. The things
you must do with caution, is cutting dovetails into a thin barrel.
I normally do it on a mill, and only go about .050 deep, which is plenty. The only things that blow barrels up is stupidity...doing
dumb things..short starting, etc. Another area that can cause problems with a thin walled barrel is installing a drum for a percussion gun(a difficult word to say) since you don't have much room for a good threaded section. There is nothing wrong with building a rifle, of any sort, with a straight barrel. In some cases
it may not be period correct, but, if you want to build a nice off-
hand target rifle, it's the way to go. They will hang nice..But...
for Swampman..they will not balance like one built with a swamped or
tapered barrel. I have always been a round ball guy, but that doesn't mean that I won't shoot a bullet gun. I have a nice "Don Brown" target Alex Henry kit I have been working on for years, in
40 cal., to shoot a bullet. One of these days I will have to finish
it......Don

donald E. Getz"

I shoot 370 grain Maxi-balls with 115 grains of FF out of my 7/8s x 1 in 30 twist.

[Norseman]

Thanks BS,
  The rifle is going to be a "Southern Kentucky" with iron furniture, no patch box but will have primo wood, a nosecap, entry thimble, butt plate and all the rest.  I figure the octagon barrel would be period correct for it.  Since the barrel is going to be octagon in 42", I was concerned with the barrel weight.  Man, if I went for a .54 cal in a one inch thick barrel for example, your talking over seven pounds just for the barrel!  I would like to use the gun for deer hunting, so the compromise for me was going to the .50 with the 7/8" X 42" GM.  I am a little concerned though, since I wanted to use it for hunting as well as re-enacting (1810'ish) that I could use a strong hunting load in it.  The slimmer barrel would look just that-slimmer, just the look on a southern mountain rifle and would be lighter as well.  What do you think, am I being logical in this and is this the correct choice in barrel?