Yep, the powder, wad and buffer are the variable I can't tack down. What I did to get an approximate idea was look up similar loads on hodgdon and, as suggested, looked at with numbers in the area of 30 grains.
There's not much difference in the recoil, really. The 1 5/8oz going faster seems like it might be a little less, but being snappier, it's probably a wash. Velocity makes my head hurt.
And, yes, we probably don't want to know how much these things kick. I was once asked as part of a job interview if I thought I could handle a .375 H&H. I guess it was pertinent because I am from SC and the job was in AK. Anyhow, I just chuckled and said, "We use bigger shells than that to shoot turkeys where I come from." Got a funny look.
