Two things right now.
1. On the Firearms draft(daft?) idea page light handgun is damage 7 while bolt-action rifle is only damage 8 although long range.
2. Shotguns can fire flechettes, they give good range and armour penetration but tend to do less damage than other types of shells. If you wanted to have these in OAGS I think they would simply have no special rules, i.e. short range is overcome, and less damage than slugs. However this might create too many possibilities for shotguns.