Big -- Here are some of my pattern numbers comparing Fasteel against Silver Steel that you might find interesting.
Pattern results from a 12-gauge 3" Remington 870 Special Purpose with a 28" barrel and factory flush Rem-chokes (pattern average of five, 30" post-shot scribed circle, yardage taped muzzle to target, in-shell pellet count average of five, and true choke constriction from bore gauge).
12 GA 3" KENT FASTEEL LOAD
1 1/4 oz #2 steel (155 pellets) @ 1,425 fps
40 YARDS
IC (.009" const.) / pattern 88 (57%)
Mod (.018" const.) / pattern 103 (66%)
F (.037" const.) / pattern 116 (75%)
12 GA 3" KENT SILVER STEEL LOAD
1 1/4 oz #2 steel (153 pellets) @ 1,480 fps
40 YARDS
IC (.009" const.) / pattern 74 (48%)
Mod (.018" const.) / pattern 112 (73%)
F (.037" const.) / pattern 122 (80%)
Hope this helps, good luck!