The 3 dram load equivalency with 1 1/8oz. shot is approximately 1,200fps.
Smokeless powders in this range for target loads, can produce around the same pressure as black powder did, however they are fast TRAP powders,
like 700X, Red Dot and perhaps Green Dot as well. Green Dot and Red Dot powders have green and red dots in the powder, respectively, for identification purposes.
In shotshells, powder like SR7625 and SR4756 can produce higher vel. at lower pressures in the 8,000PSI range as well.
800X is a slower burning powder than 700X, and is in the range of Unique and Herco, seems to me.
Having a Lyman Shotshell Loading Handbook is very helpful,
even though you have short cases. This just means you will likely have card and fiber wads which reduce pressures as well. A chronograph is handy -
but needs screen protectors if not RADAR machines. I chronographed my shotgun using shot quite effectively, without any protection, however I removed the overhead
diffuser panels and shot well over the screens.