I am attaching results of ballistic testing I had done by Precision reloading. All test loads were 20-gauge, 2.5-inch shells using Cheddite hulls and Cheddite primers. Powders used were WSF and Longshot. Some were 7/8 ounce (382 grains) and some 3/4 ounce (328 grains) of lead shot. All of the wads were obtained from BPI, and all shells were roll crimped, except the batch of shells I had obtained from Polywad, which were fold crimped. Some of these loads gave pressures in the range you indicated.
file:///C:/Users/edwar/Downloads/Edward%20Purvis%206-24-22.pdf
file:///C:/Users/edwar/Downloads/Edward%20Purvis%208-26-22.pdf
