Why the following code spawns the blueprint child of the projectile instead of the parent?

[anonymous_user_3f582bf7]

This is code from the first person template.You can see that the spawnActor is passing a class created in c++ as the argument,but in game its spawning the blueprint class inherited from the c++ class,I want to achieve the same in my game but its spawning the c++ class.

                      const FRotator SpawnRotation = GetControlRotation();
                      // MuzzleOffset is in camera space, so transform it to world space before offsetting from the character 
                      location to find the final muzzle position
                      const FVector SpawnLocation = ((FP_MuzzleLocation != nullptr) ? FP_MuzzleLocation                    
                      ->GetComponentLocation() : GetActorLocation()) + SpawnRotation.RotateVector(GunOffset);

                       //Set Spawn Collision Handling Override                  
                       FActorSpawnParameters ActorSpawnParams;
                       ActorSpawnParams.SpawnCollisionHandlingOverride = 
                       ESpawnActorCollisionHandlingMethod::AdjustIfPossibleButDontSpawnIfColliding;

			// spawn the projectile at the muzzle
			World->SpawnActor<AMyProject2Projectile>(ProjectileClass, SpawnLocation, SpawnRotation, ActorSpawnParams);