[jakogut]

The energy density and expense of capacitors, along with the efficiency of the electromagnetic coils makes them impractical.

Coil/rail guns that achieve velocities comparable to real firearms are actually quite loud, as the air is compressed and superheated in front of the projectile, which creates a report at the muzzle. However, most man portable variants are limited to around the energy of a .22 LR. Even air guns are more powerful and practical.

As an example of a weapon that's practical yet not portable, take a look at the Navy's 155mm rail gun. https://youtu.be/O2QqOvFMG_A