Any 12ga gun which I did not feel capable of handling a 1200fps 1oz load @ 7-7½K psi I would consider a total Wall-Hanger & it would never be shot by me. Lighter loads are great as long as they serve the intended purpose, but those light loads should use a fast powder.
Slow powders were not designed for extremely low pressures, they were designed to give normal shot charges a higher velocity, or heavier shot charges normal velocities, all operating at normal pressures. They generally obtain this ability by being heavily coated with a "Deterrant" which restricts burning.
Are you concerned with "Thin Bbl Walls" remember if you shoot two loads both giving a 1oz charge 1200 fps with 1 load @ 7K psi & the other @ 5K psi, The 7K load will peak at about 1" from the breech while the 5K one will probably move forward a ¼"-½" with a flatter peak & the two curves will cross at about 2½"-3" with the "Low Pressure" load actually having a slightly "Higher Pressure" for the rest of the bbl. Note also the 7K load peaks where the chamber walls are the thickest to support the pressure.
"IF" you insist on those very low pressures wth slow powders be sure and
#1-use a "Hot Primer" even at the expense of a litle extra pressure
#2-"Resrtrict" their use to warmer temperatures, do not expect them to be all purpose loads for use when the temps drop into the icy range.
You are of course totally free to ignore this & I am not a Ballistician & some loading manuals list such loads. I do note that Alliant/formerly Hercules list very low pressures only with Red Dot & Bullseye or newer powders within the same burn range & within the light load range.
