Shotgun Damage In Serenity

Shotgun damage is always a tricky thing. The abstract way many rules systems handle it is for slugs and shot/pellets to do the same damage. That's fine as a simplification, until you consider armor. A handful of small pellets will not have the same armor penetration as one, massive slug. So I break the shot damage up. For example, a 12 gauge does a d10 for slug, but shot/pellets are different:
At close and short range, the shot does 2 d6 damage attacks to one target. At medium, the shot does 1d6 to two adjacent targets and has a +1 step bonus to hit. At long range, the shot does d4 damage to three adjacent targets with a +1 step bonus to hit.

For a 20 gauge, base damage is d6 for slug and the shot damages are 2 d4, d4/d4 and d3/d3/d3