When I get around to working up loads for my 16 bore I anticipate some thing in the 4 dram range of 1&1/2 Swiss for the gun as it has an 85 inch twist IIRC. This will be for Black Bear and deer, my Grizzly plans kinda went south along with my leg. 
My 16 bore (well actually the barrel is 15 bore I suppose) shoots very well and gives good velocity, 1600 fps, with 140 gr of FF Swiss. I found in testing that there was little gain in velocity going higher. The fps gain for grain of powder used fell off. It has a Nock Breech and with the breech the barrel is 29 inches and change.
This velocity is near identical to the velocity Forsythe was getting with what I believe was a shorter 14 bore (69 caliber) percussion rifle with a (IIRC) a 96” twist using 5 grams of powder, 137.5 gr. He was using “Halls #2” which I think would have been about like our 3f. Swiss #2 is our 3f.
I calculated his tested trajectories and he was getting very close to 1600 fps.
With a hardened RB he stated it would shoot through an Indian Elephants head from side to side.
I read of people shooting modern “Forsythe” rifles in 62 caliber with 200 grains of powder and wonder why? Its a waste of powder.
If we read John Taylor’s “Other Elephant Stories” chapter in “Pondoro” we learn that when his ammo shipment was misdirected he fwll back to using a borrowed 10 bore smooth percussion gun, apparently meant for the RB. It was regulated for 6 drams (167 gr) of powder. He used it to kill “13 good bulls” and I think 6-8 Rhino from ambush near a waterhole. He stopped using it when he ran out of hardened round balls. All were heart/lung shots often in the dark or low light. He was an ivory hunter and is he did not hunt he did not eat very well.
This said most ran 100-150 yards before dropping. He stated that he would not have wanted to face a charge with it.
I also remember the account of a guy on the Knik River RR bridge west of Palmer AK. A Brown Bear come up at the headwall of the bridge and the fool (?) shot him in the heart or lungs with a medium caliber magnum revolver. Fortunately the bear ran away down the tracks about 150 yards before dying. I was living in Anchorage at the time. When I was fishing on the Kenai River at Soldotna some years back when a guy from Anchorage shot a sow Grizzly with his medium caliber “carry” handgun when the bear got too close. Head shot I am sure. The locals seemed to think it was a bad shoot. But a Gbear at close range is not something I would want .
I also have a story told to me by a friend of one of the participants that resulted in the shooter with a modern magnum getting a lot of stitches after shooting a Brown Bear twice with a pretty powerful mid caliber suppository gun both good hits I was told. Then having to do a followup which ended badly. The guy that told my co-worker the story shot the bear something over 6 times with a rifle while the bear was mauling the other hunter. They never could determine if the man’s heel was bitten off by the bear or shot off in the melee. Anyway the bear left and was still making a lot of noise as the injured hunter was being taken back to the river. The heathy one went for the boat, had to swim around a sow and cubs on the way…. But everyone survived except the bear that was recovered the next day….. He said this was the smaller of the two they started stalking on the Mtn side above the river…. The bigger one was gone when they got there.
You just never know.
Where I hunt the Gbears are smaller. So I take my chances and often hunt with a suppository gun depending on my attitude that day. And remember in many places Gbears/Brown Bears think a gunshot is a dinner bell and they come to it. So in some places if you shoot a deer or elk you get it out ASAP. Like immediately. Or you may have to shoot you way out. One hunter killed 2 gbears in one year about 10 years back. Once when he killed his Elk and another when hunting with a friend.
We had a hiker or horn hunter killed by a Gbear about 40-50 miles south of here last month. Leaving a wife and young kids…. Like I said you just never know. The bears here are a LOT smaller than the coastal bears in AK.
