Okay. Figured out why things seemed off. Sylph's test was at 7 spaces (which I didn't notice, I was thinking 8), meaning that you would see 10+ damage just over half the time, which matches the test. Which means that SoB 2 increases your odds of one-shotting a former by about 16% at max range. For knockback, I'm assuming armor DOES apply first, since the odds of getting at least 7 damage are quite good, (a roll of 15+, or about 74%) even without SoB. Which would mean that against an opponent with 2 armor (4 damage reduction vs. shrapnel), you would need 24 damage to score a knockback at max range, which is <1% with SoB at 0, 1, or 2, but jumps to 2.4% at SoB 3, and ~14% at SoB 5. Which is still nowhere near enough to take 5 traits. ;-P At point-blank range with 2 armor, the odds of a knockback are >99% to begin with, so no gain there. But a knockback 2 spaces from point-blank is 26% without; SoB 1 is 41.5%, 3 is 74%, and 5 is 93.5% and 6.5% of getting a triple. That's a little more interesting, though still pretty minor most of the time. I think the lesson to be gathered here is that SoB (of course) isn't meant to be used for shotguns, but if you're building rapid-fire, you can count on knockback with even a basic shotty in the prepared slot.

No promises on my math.

Oh, and if I had realized how in-depth this was going to be, I might not have put it on the quick questions thread. ;)