Vlad,
Try
www.rstshells.com Their shells are pressure friendly to our old Parkers and hit hard. Sherman Bell did a series of articals in Double Gun Journal titled "Finding out for myself". He studied pressure curves of black powder shotgun shells and compared them to modern powders at similar velocities. The short and long of it is pressure curves are identical when using certain powders, primers, wads and hulls. RST makes shotgun shells that duplicate black powder pressures and velocities with smokeless powders.
Harry