The heaviest smokeless powder loads listed for 12-gauge I've found in the early catalogues I have is the 3 1/2 Dram Equiv. 1 1/4 ounce. However, from much of the reading I've done, it appears that 3 1/4 Dram equiv. 1 1/4 ounce was considered a much better "balanced" load. You could get these loads in 2 3/4, 2 7/8, 3 or 3 1/4 inch cases. The longer cases just got more and better wadding.