Hello CC.

The S&B gun I have doesn`t even stabilize the ball..it shoots all over the place.

MIne isn`t a H&H with ratchet rifling like H&H, but an ovalbore or "hairrifling" as Paul said.

The H&H standard paradox ammo fit well enough down through the barrels to become squezzed just before the muzzle.
Here the barrelflats:

According to the proof-act th barrels should be marked "S&B" or a "C" if the barrels are choked, but neither is there?.

The barrels are VERY oval indeed, and the squezzes down 2,5" before the muzzle but still remains oval to the muzzle. Been measuring the muzzle with a 3 dot laser the ovalness takes a spin before the muzzle.

The gun weighs almost 8,5Ibs which suggest a heavyload ballgun, but if it isn`t why would anybody make a ovalbored gun to roundballs?.
If this gun lets say were made for roundballs, the expresssight for 100yards is very optimistic, as most guns made for roundballs often were set for 50-60 yards.
I can see this gun has been reproofed for 70mm shells, however there is a mark which I don`t understand where is says "SD"?. Any body knows what that means?.