So, if this is the effect of a railgun shot:
Another railgun test footage:
What problems can there possibly be with this weapon type? In other words, why is this still a pure science fiction weapon?
Actually, there are several problems with railguns, mass drivers and linear accelerators in general. Which is kind of obvious since you can't see them in military forces yet, except a US Navy trial weapon.
Well, the first and foremost problem is the energy required. In convensional firearms, the energy to launch the projectile is provided by chemical reactions from explosive proplellants such as cordite gunpowder. But railguns require a direct electrical power source, in fact a power source so large currenlty only US Navy battleships can provide it.
Until ways to carry and minimize the power source are found, railguns will remain exotic weapons found only on battleships.
Another hurdle that needs to be over come is recoil. Newton has explained to us hunderds of years ago that if we push something away, it will push us right back. Since a railgun projectile has so much kinetic energy, the recoil forces will be huge. Again, it may be that only something as large as a battleship will be able to realistically use a railgun.
And last but not least, the magnetic signature. Since a railgun uses huge magnetic fields to propell its projectile, the magnetic fields created are relatively easily disovered. In effect, the platform mounting and firing a railgun will be shouting "I'm here! Come and get me!" as loud as it would be able.
So, there's still some work to be done before fielding battlefield worthy railguns will become a reality but I have no doubts this science fiction weapon will become reality.