Logically, this should be posted under Reloading or General Interest but because of the interest shown in the Flues strings I am posting it here. Before WW1, shotgun pressures were held to 8000-8500 pounds of pressure- pretty much duplicating black powder loads. After the war, interest in repeaters blossomed and manufacturers increased pressures to the 13000-135000 pound level, causing blown Damascus barrels, cracked recievers and stocks. It also makes the oldies kick like a mule.
Low pressure load data are found in loading manuals and can easily be produced by anyone capable of reloading shotgun ammunition. It is commercially available from Galazine's, Cabala's or Poly- Wad. Give the old guns a break. In fact, give yourself a break. You'll be glad you did.
'Lonzo