The flame at the muzzle is real under those conditions in the shade [not muzzle blast, which is the sound and shock wave effect]. Were you to shoot in full sun or with different ammunition the flame would be different and probably not present. It is the same for just about any carbine when using full loads intended for rifle barrels. That is why current military rifles and carbines are all fitted with a flash hider, having such short barrels, firing ammunition intended for use in machine guns too.

The flame is from propellant not consumed in the barrel but outside it, thus confirming the shorter barrel needs less or different propellant. For the intended use of this carbine I suppose the muzzle flame was irrelevant. I know this milsurp ammo, but still, don't blame the firearm for the ammunition used.

Excellent photo, catching the flame just right.