Work in progress. Muzzle flash made in Unreal Engine 4 with custom textures made in Krita. Based on the muzzle flash from Rebellion's Alien Deathstorm reveal trailer - https://www.youtube.com/watch?v=_nutnEMMVmM.
Effect in Unreal Engine 4. The projectile has a simple mesh with a glow that has an activation rate of 0.3, which gives a tracer effect.
Niagara system. The main muzzle flash nodes randomise between several textures which also have a dissolve material applied to them.