When I personally think of fast steel now, it is around 1550 fps. I really like a couple of hand loads that safely go in the 1680-1720 fps range. Other reloaders consider those to be of the fast, fast variety. There is a balancing act as you're trying to get the most amount of pellets in an even 30 inch diameter pattern while delivering the most ENERGY. Remember that energy is derived something on the order of E = W x VxV x 2.218279 x 10-6
where:
W=bullet (or pellet) weight(grains)
V=velocity(fps)
E=energy (ft-lbs)

That was taken off another website which was out of a textbook so I personally did not dream it up. Go to your Physics I textbook for verification. What you do see is that Velocity is squared, meaning that the speed of the projectile can deliver more to the energy than the mass in general terms. So going from 1250 fps to 1550 fps or 1700 fps (with the projectile having the same mass) there is a significant difference.

OK that is the math portion. Prior to testing all of the loads on the the pattern boards and birds I was very skeptical. Hey, I'm a scientist thats my job. However after testing it I was happily surprised with the results. That being said if your gun patterns Expert Steel great and you have confidence when shooting it, by all means go for it. I've just watched more birds tumble head over webbed feet, or just had the life truly sucked out of them this year than ever before. Maybe I've been lucky all year. Could be, but I bet if you were to do the same test I've done you would convert as well. Good luck to all.

PS. I can't explain why HS shot ducks bleed so effusely. Really they will leave all kinds of blood in your bag. Is it more pellets? More energy? More holes (holes in and out)? The irregular shape? I don't know. The meat isn't very damaged but the blood loss is high. Any answers?