((As I recall, the Sibilus has so many capacitors because it fires the rockets at a similar force to gauss rifles, despite their smaller size. There's no problem with smaller rounds, although there's probably some small issues with inefficiency- larger rounds are cheaper by weight, and making more complex mechanisms for a higher fire rate would cost more too.
Hapah, I've had two ideas for a smaller caliber gauss automatic, ever since the Testament was nerfed. First, an
FN P90 shaped SMG that fires a
9x39mm projectile at subsonic velocities (which effectively makes it suppressed). A 9x39mm projectile has similar dimensions to a full 5.7x28mm cartridge, is designed for subsonic velocites, and maintains excellent accuracy and armor piercing capability at those velocities. Of course, it'd effectively be a hollowpoint, considering light body armor in ER stops
20mm rounds, and it would do less damage since real 9x39 is primarily lead, and this would be a lighter material since it needs to be magnetic. Also, you'd have to fit gauss coils inside the P90's frame, which might not be possible.
The second, more realistic idea, is basically a gauss LSW. Make it 5.56, and assuming ER 20mm has similar dimensions to real life 20mm, you could get 250 round magazines for the same material cost as the gauss rifle mags. It has the same problems as the above idea though, and doesn't even have the advantage of being silenced. And it would probably cost three tokens, one less than the Testament, which has absurd AP ability, and only somewhat worse ammo economy.
That was probably more information than anyone wanted, but there you go. Anyways, I'd suggest you not even look into low caliber gauss weapons, except maybe for use as SMGs. Lasers are basically entirely superior.))