I'm cross posting this, because I'm not getting much responce.
I just loaded up 50 rounds on my Grabber, 16 gauge loads.
Winchester Super X hull, trimmed to 2-9/16"
Win. 209 primer
75 grains by Volume of 2F Pyrodex, used the #46 bushing
One 1/8" nitro card
One 3/8" Fiber wad
1 oz. #8 lead shot
6 point crimps.

I found a known tested load very close to this, except they used
regular 3F black powder. It tested out at 1200 FPS @ 5000 PSI.
Care to guess how the 2F Pyrodex will compare to the 3F BP.
Thanks, Dave Miles