Dave: I've got a note that a 1891 12g Parker was patterned with 1 1/4 oz. No. 7 and 42 grains (3 1/4 Dr. Eq.) DuPont Bulk.
Bruce Day posted a 1900 Parker hang tag stating that 12g 2 5/8” chambered guns were patterned at 40 yds. in a 30” circle using a 2 5/8” shell with 1 1/8 oz. No. 7 chilled shot and 40 grains (3 1/4 Dr. Eq.) of DuPont Bulk Smokeless powder.
DuPont Bulk was originally 40 grain = 3 Dram Eq. and "New DuPont Bulk" was 37 gr. = 3 Dr. Eq.
At the turn-of-the-century, W. R. Crosby, professional rep of the Baker Gun Co., then Hunter Arms, and later Parker was using 44 grains “E.C.” powder (3 1/8 Dram), 1 1/4 ounces No. 7 1/2 shot in first barrel and 1 1/4 ounces No. 7 in second barrel, loaded in Leader shells by the Winchester Repeating Arms Co.
U.M.C. Arrow Trap loads. I think they were still 2 5/8" then
Hybrid Mode