User blog comment:AugFC/An in-depth look at AW's weapon design/@comment-24756040-20141227215353

Don't forget one thing about the S-12's drum mag: it's holding 12 gauge shells, not regular bullets. In comparative size to a bullet, 12 gauge shells are pretty big, so it only makes sense it has a smaller mag size. It can go up to a 15 maximum if you're using Extended Mags on the right variant if that's more realistic. As well, you have to account for how fast the S-12 shoots. With 12 gauge shells being fed from a drum mag, and they're being shot at with such a high cyclic rate of fire, going larger would make feeding very unreliable.